Hi, I know this probably isn't the right area of this forum to be posting this question, but I was hoping some of you classic bike buffs might be able to help me...

I've just tried to adjust the height of my handlebars (by unscrewing the top bolt and tapping with a hammer to loosen). This worked fine, and my handlebars are now loosened - but when I tried to tighten them back up, there was nothing to screw the thread back into - have I whacked the bolt too hard?
The thread is now completely loose and being unable to re-tighten my handlebars, I can't use my bike at all, which is a problem since it's my only form of transport. Any help would be hugely appreciated!