It's more like borrowed than stolen though seeing as how you are on it, are you certain sure, like Ramones says, that you didn't let someone else have the use of it whilst you were gone. Going by other posts you have made, that is what you have done in the past.
But if it has been stolen, that is the 4th time I have heard of someones account being stolen since Christmas! I don't understand why more can't be done to prevent this or why the devs can't just return stolen accounts and ban the person using them from the game. It may not stop it altogether but it would certainly be a good deterrent.
Ahh Loftar, it is happening so much though, why can't you make a public example of ppl who steal others accounts and ban them from the game?