Alls well that ends well!
Something similar actually happened to me last week. I was planning on going out after work, so I dropped acid while still there. When I was leaving the piece of foil that had 5 hits still in there must have fell out of my coat or something. I was locking the place up with this other dude and I couldn't say "hold on I lost some drugs", so I was worried that I lost it for most of the night.
Went back the next morning because I knew the place was getting cleaned. I showed up and was checking out possible places it could be when I started chatting with someone who was sweeping the floor. Couldn't have been four feet away from where he was and I saw the little piece of foil! Success!