Given the info we have in this thread, I wouldn't bat an eye. There are plenty of legit reasons a school employee would get a child from a classroom - many of them mentioned already. Said child's parent is coming to get her for a dentist appt. Said child has to go to the office for medication. Said child is in trouble for something and it is going to be discussed. Said child has an eye exam, speech therapy, lice check, could be a million things!
I get the feeling that if it had been a female principal, this wouldn't have been an issue. If the OP had said she had seen kids taken from class before, but this specific time gave her red flags - well, that I'd understand.
The fact that she felt the kid hesitated - again could be so many things. Maybe she was involved in something she enjoyed. Maybe she didn't want to miss something about to come up. Maybe she doesn't like taking her medication. Maybe she wrote her name on the snack table and knows she might be getting in trouble. Maybe her art submission won and the paper sent a reporter to take a photo of her for the local paper.
It feels like it isn't this specific incident that is bothering the OP, more of a nervousness about entrusting her child to other adults. If a principal was going to abuse a preschool kid, don't you think that person would do something a bit more subtle than pulling her out of class in front of a teacher, a parent volunteer, and 24 other kids?
I work at a small, private elementary. Our principal - who just happens to be a large man - pulls kids out, individually or in small groups, for a variety of reasons. It is usually to discuss something that would be embarrassing to the kid to discuss in front of the class. He is very respectful about their privacy. We also have had kids on a variety of medications that must be administered at school. I pull one little girl out many times a day to get a blood sugar reading on her as she is diabetic.
In the OP's situation, I would do nothing.