Lost equipment quest?

I got an email near the beginning of the game shortly after starting Chapter 1 saying to check the Abandoned Factory for some lost equipment. I think this is one of the quests (I have completed 57/60, and I know I still need Speed Star and Resistance Recon), but I can't seem to start it.

When I Chapter select to various points in the game, I see a red dot where 9S and 2B fight the first goliath in the prologue. However, when I try to get to the dot it disappears. It doesn't matter if I transport or walk, the marker disappears when you cross the overpass to the portion which heads down into the factory entry.

Also, does this count as an actual quest (shows in Quest List and against the 60 available)?

The quest markers sometimes disappear when you're close enough to the quest objective (if memory serves).

Either way, you're looking for the Virtuous Treaty that 2B loses in the first chapter of route A. You will find it if you go as far on the broken bridge as you can. There will be a sword sticking out of the ground and you can pick it up.

If you want visuals, here's a video of where exactly to go:

According to this list of side quests, this isn't on the list, so I don't believe it counts as one. If you already have the Virtuous Treaty, you should be good to go and can just ignore the marker for this.