It would actually be easy to check if the timing belt was changed - just pop off the top half of the cover and read the stamp on the belt (might need to crank once or twice to bring the stamp to the top). I would be a bit surprised if even the most dishonest shop would do this, because if the factory belt breaks it would be very much a very smoking gun in plain sight for any other mechanic to see.

Far more likely is that the other 3 parts in the belt loop didn't get changed along with the belt itself. Many of us who DIY are well aware that the early Aveo timing belt breakage was actually mainly the result of a bunch of bad pulley bearings. And so it's become fairly common practice in the DIY community to change the pump, and 2 pulleys along with the belt. The parts guys are on board with this, with most of them selling kits with the 4 parts packaged together at $100 or less for all 4. But I think that changing everything is far less common for shops because the price for the belt job alone gives most customers enough of a sticker shock so that they don't even want to consider additional $$ on top ot that. Not blaming the shop mechanics because it all goes back to designing the belt in such a way that causes it to be a time-consuming job even for a pro. And that commentary is of course not limited to Aveos - I know first-hand that changing a Honda Civic belt ain't no bargain either