But the agent who enticed me here had no job for me, though she gave me a free room and free use of the company's office equipment to help me search for a job.

I wonder if you were offered a job by that agent before you underwent your long, and subsequently fruitless, train journey from Guangdong to Yuncheng. I suspect the vacancy was urgent, and was offered to you orally. As old China hands know from bitter experience, oral job offers like that one can fall through, as indeed verbal promises can!
But what would undoubtedly be very useful would be the name of the Yuncheng agent who enticed you to Yuncheng. Then we can give her a wide berth. Can't see it being EV, but I did hear there's a Chinese woman aka Jane? with an office across from the main bus station whose speciality is supplying elementary schools with foreign teachers. Her boss is a Chinese 'businessman'. It is said that quite recently two of your fellow countrymen used her office keys to remove and reset computer office equipment to try to recoup some of the salary they'd been duped out of by her. After that, they took off hastily, but weren't reported to the police, probably because they were employed on illegal visas. That is not to say that there aren't other foreign teachers in Yuncheng and its associated counties working illegally too! The thing about those geographical areas is the Yuncheng PSB won't investigate such matters, and the local police won't either, especially not them. You can be sure that this situation has been 'arranged' by the local Chinese agents before they recruit foreign teachers wih the wrong visas. Enough said, methinks. You can use your imagination to give you the reasons! I guess that Yuncheng has hordes of Poles/ Russians and Africans teaching with F visas, I've met quite a few here. But it must be obvious to the authorities here that there isn't anywhere near the local diversity of factories and production to warrant so many F visa holders being here! A bit of a joke really, but joking apart, wherever you go to in China, ensure you have enough cash to exit the country at very short notice, should that ever become necessary. Security of employment can be a major issue for those who aren't passport holders of a 'big five' country! For those who don't know which ones they are, the list comprises the USA, the UK, Australia, Canada and New Zealand. If you're not from one of them, it can be hard to get a Z visa, seemingly.
Yes, the multitalented and versatile Mr Rivers is back. He's very good at matching a given foreigner with a suitable workplace and a t/a who won't make a teacher's life a misery. In his absence there were more problems of that kind, so he was tempted back by the good doctor, though it would surely have cost him more money to have done so!