They can't live in the suit, Once they are out of it, presumedly in an Inn or something. A thief crawls into a window and enters the armor. once they are in they run away, Jump out of the window and use the antigravity to float away...
It's kinda cheesy, but just make up for it somehow.
I've always gone with "what is rolled is Rolled" when it comes to magic items, but in some cases, the Magic far outweighs the levels and needs to be accounted for. A Zirconium suit would be news, and many Much Higher level people would probably want to track it down, and so would the original owner.