Babysitter troubles?

Something is bugging me.

As I was picking up my kids from the babysitters, she went to the basement to get them and she started yelling at a kid.... she told him that he was "not a nice boy" and if it keeps up she doesn't want him in her house, and that she was going to have to talk to his mom about it.

Then  her and my kids came up stairs and everyone was taking and happy and we left.

When we got home, I asked Quintin who was it who got in trouble at Wendy's.... he said it was him.   I asked him what the heck he could have done to prompt such a reaction from her.  To me, saying "you're not a nice boy" and "I don't want you in my house" means that something very serious has happened...being violent or blatantly disrespectful, for example.   It took a while to get any sort of a story out of him, cuz he was crying, but he insists that he just said "Yay" really loud and was running in circles, when he found out I was there.   I asked him what else he has done to get in trouble, because this is obviously a continuing problem and he says he just doesn't remember his manners.

Now, either he isn't telling me the whole story, and I am inclined to believe him, honestly, because he IS a nice boy with the exception of not sharing with his brother from time to time.... Or, we have a problem with Wendy either or reacting or being extremely strict in her expectations of a 6 year old kid.

Telling someone he's bad should revolve around a bad offense, don't you think?  Telling someone you don't want them in your house means that they've seriously offended you in some way.   What the heck could my kid have done to warrant that?  Does bad manners warrant it?

And what the hell am I supposed to do if she says she doesn't want to babysit him anymore?

I'm just heartsick at the idea that someone thinks my kid is a "bad boy", cuz he's not.   I don't want to think that I'm being blind as a mom, but is it possible I am?   Have I missed something serious?  

Now I'm mad at him and I don't even know what/if he's done anything...I'm being super critical of his behavior thinking that it must be my fault...maybe I've been too lenient.   Obviously, I need to talk to Wendy, but I won't be able to until Tuesday now, I don't want to bother her after hours. Sigh....

I hate feeling like this, it makes me sad and angry at the same time.