Help...bolt is spinning with the nut

So I got my OME suspension from wheelers today. Driver side went in no problem. I put my passenger side strut in and while I was putting the top nuts on I realized I forgot to put the spacer in. No problem right? I only had them about half way on so I start to take them off. I get the outer two off then start to work on the one closest to the engine. Well the bolt is now spinning with the nut. I can't tighten it or loosen it. What do I do?! (I realize now that my title sucks.)

 

Thin grinding disc. Cut nut and bolt off.

Take it apart and put in a new top cap or tack weld new bolt to top cap.