Update: I found them.
Unfortunately, it's pretty anti-climactic and hard to describe.
Short version: they were in the limited area I'd said they pretty much had to be in, in an area I had searched repeatedly.
It was the restroom. I have a package a few inches wide and some junk around it and guess it hadn't looked like the keys could be under it, but they were. A picture might make it clearer, I'll consider it.
It was just a freakily hard to find case that's not very satisfying, frustrating when you thought you had looked carefully. Of course they were there nearly 2 months before I found them, inches away daily.