I was on floor 10-2. Dropped a couple of relics (about 10) on the ground near the relic shop to buy some unwanted relic and go sell them to the Mystery room guy that buy them (I had the supply box, I was farming relics to get those I wanted). After a couple of buy/sell run, I came back to my dropped relics to found out they were mostly gone. About 3 relics were remaining, the other ones went POOF with no reason. (The drop spot was really far away from the mystery room, I suspect that the mystery room guy ate my relics, but I never got a huge sum of gold to indicate that.