Categories somehow dissapearing?

okay, I don’t know wtf happened, but I’m suddenly switching servers, and have been having some WordPress problems. The most recent one, was that all of the categories on my blog got deleted. Freaking deleted out of nowhere. I’m the only admin, and I have one other author, but that’s it. Does anyone know what happen?

Also, I don’t think it was happening because I know of the hacking craft myself and have big passwords and programs and stuff.

Thanks,
Keenan