First of all, why did you have coolant in the car - had anything else been done to the cooling system recently, or had you been losing coolant? Next, always give the year and mileage - there have been reports of t-stat problems in the later models, and the older ones have the POS plastic t-stat housing which have caused lots of problems for many owners.
Although this MIGHT be air in the system, my guess would be something else because Aveos bleed easily (as compared to some other vehicles), and any half way competent shop should be able to get that done correctly. My guess would be a bad t-stat, unless there had been something else going on that you didn't mention in your OP. You didn't say anything about the current coolant level - is it where it should be, with no visible drips?
But that problem (whatever it turns out to be) might be the good news, because there could be much worst news on the horizon. Having given your engine a steam bath, it's become unfortunately likely that amount of heat has resulted in the head gasket starting to go. I hope this is not the case, but you will need to monitor the coolant and engine performance closely going forward (after you fix whatever is wrong right now).