You saw a teacher paying for everything? Sounds like he is grooming to me.

Please don't get paranoid about being ripped off. My chinese mother in law always tells me that I pay to much. Yes she buys things for less, but it is a war of attrition with market vendors who in the end give her the lower price just to get rid of her. It is a tactic that only works for old people.

I have hovered around market stalls, listening in to other shoppers, and generally pay the same price as locals.

Try wandering around a market and asking several vendors the price, there is little if any deviation, as I think they agree prices before the day begins. They will not have agreed any laowai price, we are too rare.

Sometimes I get a better price than my Chinese wife.

Where I have been cheated is on weight, they charged for 1kg when it is just over a half. Easy to spot vendors who turn the face of the scale to them, not turned to the side where you can both see.
If you shop regularly, you will build a relationship with a couple of traders.

@faraday
Maybe not called capitalism, but I was taught that the idea of the 'free market economy' was born in England during the industrial revolution.

@misfit
If someone runs a school and customers/parents do not want brown/black skinned teachers, and there were plenty of other schools to choose from... What does the owner do? The fact that ABC/BBC/etc. make better teachers is irrelevant. There are far better food choices than the ubiquitous McD/KFC.
Your point about 'unqualified laowai' is also contestable. I wish people would not feed the urban myth. In 10 years I have only me one person who was not qualified.

It is the plumbing in the building. You can't control that.
We had a similar problem in shanghai with one of the neighbors keeping a dog on the balcony and pushing the dog poop down the drains. It might also be a neighbor peeing in the sink to save water. You can't control others in the building either.
I would move. Put it down to experience and next time check for smell before renting a place.

Another thought.
Your files may now be hidden. I have had this with a compromised thumb drive.
If you use Windows, somewhere in the control panel you can go to the drive and 'show hidden files'. They may then re-appear.

At least in NZ case it was a genuine mistake and they fessed up and did something about it, even though it would hurt the business.
Unlike other cases of deliberate tampering.