I was playtesting on a server with some people and when i killed an enemy (in pit on A site) i noticed that his AWP fell through the ground. I was unable to get it back so i tried to recrate it and found the spot. It seems to be the middle part of the doorway on the bottom.

*Seems to happen to most if not all guns and nades but the bomb seems fine.

https://www.youtube.com/watch?v=-udWdUs9APE

I recorded it just in case you weret able to find it. Sorry about the bad video quality i dont know what happend.