Ahh. That makes sense.
If the belt broke while they were trying to start the engine, there is a slight chance the camshaft was in a position to have no valves fully open, so it's possible they aren't bent. What I would do is prepare the owner with a worst case estimate that involves removing the cylinder head to have the bent valves replaced by an engine machine shop. Very few do-it-yourselfers and few repair shops have the special tools needed to do that part of the repair.
Once you get the okay to do the work, turn the crankshaft only by hand, not with the car's starter, until it's at top dead center, then back it up about five or six teeth on the sprocket. That will insure no piston is all the way up. Now you can safely turn the camshaft by hand. Bring it to top dead center according to the timing mark, then you can bring the crankshaft back to TDC. Put the timing belt on, then rotate the crankshaft two complete revolutions by hand in the normal direction, and stop at TDC, then double-check the timing marks. If they're correct, you can do a compression test. The actual values aren't important at this time because to be accurate the engine should be warm. All you're looking for is do you have reasonably good compression in all the cylinders or are any real low.
If you have compression the engine can be run that way with the covers removed. I like to see it run before I take the time to put everything back together in case I made a mistake. This gives you a chance to see if the belt is tracking off-center on any pulley or sprocket which would lead to another failure.
If you get lucky and don't have to replace any valves, you get to surprise the owner with a bill much lower than expected. Who doesn't like that?
Friday, October 19th, 2012 AT 7:11 AM