i have seen some pretty nasty stuff too, working at grocery stores and retail you see some pretty bad stuff. We had one where there was poo on the ceiling. I have no idea how that happened, don't want to know.
Anyway, here is something i figured out to do. Since i have an ostomy the smell can be a little stronger, so i was trying to think of something i coudl do to help kill the smell, well you know those little bottles of spray breath freshners, like bianca? they are really small and will fit in your pocket. Well, they have a pretty high concentration of alchol in them, which means not only do they kill the smell, they kill the germs! so when i get in a public batrhoom, i just spray it on the seat, then wipe it off with some tp, then the seat is at least somewhat cleaner. and as long as you spray it before you make the smell, it hides it really well.