to be sure, take the oil cap off, get an assiastant to turn the engine over for a second and peer down the oil filler hole If the camshaft moves it OK and must be something else, if not the belt has gone.
Unlucky mate, full sympathies your way and to any other alfa owner with any problems.
Had mine changed by my mate at around 60000 miles. I think I was well lucky changing it this late...so...far. Belt was actually fitted backwards, but we couldnt be bothered to fix it...he said it should be ok.
Touch wood my beloved 146ti has been a dream (apart from battery going flat if left on drive for 4 days or more ?? ). I had cambelt & tensioners done just before christmas, by Deens @ Hampton Court. Car had covered 82,000 dreamy miles ;-) I Cannot reccommend Deens highly enough ;-) Oh and very very good price aswell ;-)