I have had a few people tell me this about their children. It kind of makes sense because there is more mucus and saliva while teething and they could just be gagging on that and throwing up. They said their kids would just be playing and puke and they often didn't even realize it at first.
I know my son did. He had also NEVER had a diaper rash until now when he is teething. His doctor said that when they are this little that anything (but especially teething) will through their whole digestive tract off. Good luck and it will get better.