I wouldn't worry about copyright, but trademark
If they actually bothered to register the name as a trademark -- (R) instead of (TM) then they can prevent you from (re)using it. Worse, they would legally be *required* to take action to keep you from using it, since undefended trademarks are declared void and no company wants that to happen.
Now... technically you used the name first and may have some proof of that (your game floating around the internet), but if you never contested them from using it for their product, you may have essentially given up your rights (and claim) to the name by now.
You're in really fuzzy territory at the moment -- if you care deeply enough, consult with a trademark lawyer to find out what your standing is, never take legal advice from strangers over the internet. :->
If they actually bothered to register the name as a trademark -- (R) instead of (TM) then they can prevent you from (re)using it. Worse, they would legally be *required* to take action to keep you from using it, since undefended trademarks are declared void and no company wants that to happen.
Now... technically you used the name first and may have some proof of that (your game floating around the internet), but if you never contested them from using it for their product, you may have essentially given up your rights (and claim) to the name by now.
You're in really fuzzy territory at the moment -- if you care deeply enough, consult with a trademark lawyer to find out what your standing is, never take legal advice from strangers over the internet. :->