Sounds like the belt may have been loose enough and skipped teeth. Usually the only way to have ZERO compression is bent valves. Bad HG, pistn ring, etc will usually be somewhere between 50 and 130. The good news is you can get a head rebuilt for ~200 bucks, and new valves are about 200 for SS, so stock should be around 100--150 I'd guess. And while the head is off, you can do the HG fix, and if it needed timing belt parts replaced or will soon now is the time. Also be SURE this asshat does the tbelt tension right. One does not just go in and "tighten" the tbelt on a DSM. MAybe on every OTHER import out there... But not a turbo DSM. The tension has to be set such that the gap bewtween the tenioner arm and tensioner body is between .15 and .18 inches after it sets for about 15 minutes to expand fully. Read the vfaq, and make that toolbag read it twice, as I suggested earlier. Its no wonder people think that DSMs are unreliable when I consider the douchenozzles that are working on them... Its not really thier fualt either, they just dont realize thats its a very different system than all other cars out there.
At least give him the info I gave above about having that gap right. I've done this too many times, and it still takes me half a dozen tries to get the gap in between .15 and .18. He should know how to change it (tighten the tension to get the gap smaller, and vice vera if its too small) Good luck.