Get a torque wrench and turn it slowly until it starts to budge... if it's a set T.W. then start around 50 and work your way up until it moves... that should tell you how much it was torqued to...
Good luck..
It wont be exact, but it will get you in the ball park. It takes more torque to "pop" the fastener loose than the original value it was tightened down to. How much depends on all the variables possible. Oil or moly lube, clean threads or gritty/tight, lube under the nut's head or not, etc...
65Shelby is right on - you can't check to see how much it was torqued to because of "stiction" - the force required to break the threads loose is and start the bolt turning is signficantly greater than the force used to tighten it while it was turning. If it was significantly undertorqued - putting the wrench on it and pulling up will tell you that it was left short. Otherwise, the best you can do is to either trust that it's right - or slightly loosen the fastener, and then re-torque to the proper setting. Don't kid yourself however - setting your clicker wrench to the proper setting and pulling on the fastener to find that it 'clicks' really doesn't tell you much of anything if someone else fastened it in the first place.
Edit - and my comments refer to the bolt on the stud, or a head bolt. The stud itself should not be torqued into place. It should be thread sealed, and simply hand-tightened into the block.