did I lose everything on my portable harddrive?

My friend wanted to borrow my portable harddrive so he could watch videos on his xbox. sure no prob. according to him he never unplugged it or moved it. didnt have any problems. about a week ago he decides to move his xbox to a different spot in his house. goes through the whole "unplug everything" process and what not(also unplugs my HDD). he sets it all back up and plugs my harddrive back in. "No video formats found". "Weird" he says. he unplugs it and hooks it up to his laptop. I had named my drive so that what he was looking for. instead he gets "Removable disk f or whatever" and finds my 300 gigs of random stuff....wait for it....GONE! clean as a whistle!

does someone want to tell me what the F happened?