You have my sympathy. This can happen to anyone, not only an older teacher. The internet and local ethical values are most likely to be blamed here. Local employers have no shame and the internet only enhances their poor potential. If I were you, I would use the visa and seek another opportunity at some University. I strongly believe there are going to be quite a few Uni employers in a somewhat similar situation as you are. Teachers don't show up too, do they? In my school a FT came for one day, and then he decided to make a broad daylight run. I saw him ,or shall I say walking, with a smile and a cooking pan to a bus sop. The local market is a huge jungle and the regulators have only added few more local monkeys in.
Cheers and beers to crocs and monkeys in mainland education :)