those "recovered" files could be almost anything. you can safely just empty the trash and not worry about it. they are just files that the os thinks were lost, and most of the time they are just cache files that the creating apps deletes when you quit anyway. you will get them more often if you empty the trash right before shut down, or have a lot of apps open when you do a shut down and so they get killed as opposed to completely quitting as they like (so i get them all the time.).