How do secret rooms work in Wrath of the Lamb?

Without the DLC, the secret room would've been here guaranteed, as it's the only non-room area with three or more rooms around it:

Instead, I lose. I get nothing. Good day, sir. Why is that? What changed in the DLC?

Solution 1:

Super-late answer go!

Secret Rooms always spawn adjacent to three different rooms whenever there is such a possibility. Super Secret Rooms try to border only one room, but they are placed first.

The answer is that the Secret Room is either below the treasure room, with a Super Secret Room below that, or to the right of the shop, with the Super Secret Room to the right of it.

And to answer a comment, as I can't comment yet:
@Kappei good point. But wouldn't that in my example mean the top secret room was only adjacent to the actual secret room? – Zommuter Jul 21 '12 at 7:06
No, it means that wherever the Super Secret Room is, like two squares below the chest for example, it didn't create a possible location for the Secret Room with three adjacent rooms. So from this you can conclude the Super Secret Room is not one square below and two to the right of the chest, as that would have resulted in the Secret Room being one below and to the right of the chest <inhale>.

Solution 2:

Assuming this isn't a bug, you didn't find it.

Sometimes Secret Rooms are attached to curse rooms now, which confounds things a bit.