How to counter Protoss' fast expand as zerg?

By "Scout around 9" I assume you mean 9 supply, not 9 minutes. If a Protoss is going for a Forge First Expand build (which is quite strong) there are a couple of options available to you.

Taking a Third

Going for a third is definitely a solid choice (see IdrA vs MC in group play at MLG). Because he's going to be investing heavily in infrastructure you don't have to worry about early game Harassment or some sort of 4 Gate timing push, meaning that third base will have kicked in before your first engagement. If for some reason he does try to push after the fast expand, you can expect a largely Zealot heavy force as he won't have had resources to invest in mining Gas. Regardless his force will not be strong because of that additional investment. As a Zerg you can saturate faster, so if you get down that third immediately, you should have it up and running around the time he gets his second going.

Protoss Punishment

Know your Protoss

Now, let's say you want to punish a fast expanding Protoss (which I LOVE to do). First you'll need to recognize what kind of fast expand he's doing. Most Protoss favor a 1 Gate expand because it allows them to get early Sentry/Stalker for defense, and because it is easily confused with a 3 Gate expand which allows them to put on major pressure. There did used to be a 4 Gate fake expand, where the Protoss put down a FE and then canceled at the last second, but this has fallen out of favor since the Warpgate nerfs in 1.3.3. Telling the difference between a 3 Gate Expand and a 1 Gate Expand is tricky, and you can rarely get a 'ling scout after he gets up that first Gateway. Frequently I will sacrifice an Overlord at this point (I have nightmares about 3 Gate Expands), but you can also look for the timing on the Nexus. Many 3 Gate Expands will try to get out a Zealot + Stalker before expanding, but 1 Gate expands almost universally go Sentry first. This isn't a guarantee, but I have noticed the trend rather strongly. Finally, there is also the possibility that he's going Forge First (as the player was in your game). This is usually a very early expansion with a Photon Cannon to stop ling run bys.

In the case of 3 Gate, you'll want to play a little more defensively as that is still a decent push, but if you macro well you should be able to hold it off with your 3 Base up. On the other hand, if he goes FFE or 1 Gate, there are some nice ways to counter.

Zerglings

The purpose of that first Photon Cannon in a FFE is to stop Zergling pressure... one of the ways you can counter this is with Zergling pressure. This may seem counter intuitive, but the goal here is to run Speedlings past the range of his Photon Cannons, and into the Expo mineral line. This won't do the kind of Damage you need, but it will prevent him from getting his economy up and running. A great Protoss will handle this by building Zealots and Stalkers, but most Protoss aren't that good and will respond with more Photon Cannons. Ideally, you want him investing money in Photon Cannons (which he can't use aggressively), while not getting his economy up. This will put you largely a head (especially off 3 Bases), and allow you to dominate him in the mid game (Zerg's strength), with a 200/200 army (and maybe some drops if you're feeling creative).

Roach Play

An alternative to Speedling pressure off 3 Base, is to instead go for 2 Base Roach play. As I mentioned earlier you can easily saturate your 2 Base faster than he can saturate his, so you should be able to get a strong, early Roach ball going. I like to make a nice push around 7 Minutes. Chances are he won't have had time to put together a large army, as his second base will just be kicking in and he won't have recouped his earlier investment (bases take a long time to recoup). In this situation you can abuse the fact that Photon Cannons mean you can dictate the point of engagement. With a little Brinkmanship you should be able to catch his army out of position and snipe his Photon Cannons, or push into the Expo.

If you don't like trying to do the "back and forth" dance, you can always push for early drop play. His heavy economic investment means that he won't have a large army and some well place Zergling (or Baneling if you're feeling naughty) drops will really tear holes in his economy.

Banelings

Finally, you can always go for the classic Baneling bust. Traditional Baneling bust, was off of 1.5 Bases, at around the 6 minute mark. If, instead, you wait and go off a solid 2 Bases with a Macro Hatchery, you can bust at the 8 minute mark with an absolutely absurd amount of Zergling/Banelings. One of the hidden truths about Protoss, is that their natural clumping, combined with the small size of Zealot/Sentries, means that Banelings actually do decent damage against them. What's more, they'll largely clear out Zealots and Sentries, leaving only Stalkers for your Zerglings (Zerglings LOVE Stalkers, like every time a Stalker goes to a Zerg Frat pledge party, they have dozens of new Zergling pledges clamoring for attention around them).

Now this hasn't been, by any means, an exhaustive list but it should give you an idea of what kinds of responses you can give to early Protoss FE play. Keep in mind, his army will be weakened for a short period of time (till about 8 minutes) compared to the standard 4 Gate Protoss, and he'll rely heavily on those Photon Cannons for defense (which are not a great investment). Look for holes in his defense and Macro hard, and you should be able to make a good game of it.

On a side point about Zealot/Archon. I'm not sure why people think this is a good combo, but I usually count that as a free win. Zealot/Archon is not extremely mobile against flyers so any Muta harassment play dominates it, and it turns out it's pretty bad against Roach/Hydra as the range of the Archons doesn't let them engage the Hydras, and Zealots are terribad against Roaches. As someone who plays Templar tech Protoss, I do not recommend it. I realize you sometimes need something to tide you over till you get Storm, but consider Colossus into HT transition instead. It's a longer build, but fair more effective.

I'm only a newbie, but most protoss FE's I come accross makes it easy to drop a Nydus in their main with a Roach Ling combo. Also because they are heavly defended at the front they usually have artossis pyloned themselves.