[EZ2Luv]

First of all if they are witholding information about how your child is doing that would be enough to be looking for a new day care.
As far as any abuse I would be livid at the thought of it, but I was also first have the child checked for a UTI as someone mentioned. You say that he is not fully potty trained, could he be holding in his pee? That could cause some urinary tract issues. Then based on what the doctor says I would do one of two things, have a serious talk with whoever runs the daycare and demand that you be updated and notified about how your child is doing or search for another daycare.
If there proves to be any abuse then report it as I am sure that any pediatrcian would too.
I don't blame you for being upset. You know your child best and how well he communicates though some children can be quite imaginative. Even still you need to get the truth.

EZ