Files appear in trash when flash drive inserted
I have an 8 GB Cruzer Switch flash drive with about a dozen Xcel files on it. These are files that I have just on the flash drive rather than keeping them on my hard drive. I just noticed that when I insert the flash drive into my MacBook Pro four files will appear in Trash, two of which have names of files that are on the flash drive and two that have the name of one of those files with a time after it. When I eject the flash drive the files in Trash disappear. No other flash drive does this (same and different brands).
Does anyone have an idea what's happening here?
P.S. Each of those files have the same modified date, different times (aprox 10 minutes apart), and are the same size.
MacBook Pro (13-inch Mid 2012), OS X Mavericks (10.9)