Okay, this started out as me messing around witht the GTS to see how it worked. Long story short, I accidentally ended up uploading my Croconaw. Well, I couldn't figure out how to take him out of the system (Still can't for the life of me.) and ended up deciding to trade one of my own pokemon for it, since it was one of my best pokemon in that stage of the game. My only pokemon that fit the bill was a Delta Grimer.
So I ended up trading the Grimer for my Croconaw which ended up crashing my game.
Upon rebooting the game, it said the trade had been accepted, however when I went to my PC, I found out the Grimer was still in my party, and a new identical Grimer was in the PC, and my Croconaw had been deleted in the process, sadly.
I would like to know if this has happened to anyone else or is this something I just happened to mess up.