Unfortunately, I do hear about this a lot on the daycare lists I frequent. A lot of providers simply can't stand crying and they are ill equipped to know how to help the child that is that upset. It's unfortunate that she was unable to figure out he was in pain. There are usually signs that an experienced provider would be able to see.
It's also very common for providers to put a 2 week trial clause in their contracts. If they just don't feel the child is fitting in they feel they should ask them to leave. I would be horrified if I was unable to help a child to become comfortable with us.
I have also had the opposite experience though. I've had kids that came in and cried hard at drop off time and the parents would not even give it past a few days before they assumed something was very wrong and they tried another provider. Some kids just take longer to calm down and notice that the other kids are having fun.
Did she really say she doesn't want him at all?! If so it's good you are finding out now. She sounds like she doesn't have the skills that she needs. It will be even harder for your son to feel comfortable in the next situation. If at all possible try and find someone that has had experience with this sort of thing and I always find it best to just do a full immersion from day one. Doing a few hours and part days are more confusing for a child. They are fine in the couple of hours and then when they have to do a full day they don't understand why it was so much longer. That's my experience anyway.
Suzi