If it is not obvious when it is parked and not running, It will be obvious when it is running or being ridden. Let it for a while and see if anything comes loose. If not ride it and see if anything is loose. Bring it with you on the ride and the proper tool to reattach.
Get a service manual and get your hands dirty. This is the best way to get to know your ride.
Good luck

 

Come on now...... He said it was a "NUT".........not a bolt.!!...

If its from Ur bike it has to have a bolt or stud to screw onto, somewhere...
Shouldn't really be to hard to find...
IN all my yrs of wrenchen I don't ever remember a nut that just fell off on anything while it was just sitting....

U got any friends that like to play jokes or have U or anyone else been working on something else in the garage..???

 

I was just sitting on my fatboy once, while having a few cold ones. I fell off. Least I knew where I came from

 

Take time to get to know the machine...
http://www.youtube.com/watch?v=UpOBgvHmqf4