I keep my iTunes library on an external hard drive. Today I was deleteing matched low bit rate songs so I could re-download them from iCloud with a higher bit rate version. I select the option to remove the song from my iTunes library and I select the option to delete the song and move it to the trash. The song is then removed from the iTunes interface as well as the hard drive (when I go to the file location on my hard drive it is no longer there). However, when I go to the Trash bin, the file is not there leadng me to believe the file has in fact not been deleted.
I've also noticed that when I sync my iPhone and have all the newly updated apps transfered to my iTunes library, the old deleted files no longer appear in the trash been as they used to.
FYI - I'm running the newest version of iTunes 10.