Thanks guys he's getting moved right now. He hasnt showed any signs of wanting to breed her, but like you mentioned im not out there all night long. I am a stay at home mom so im home all day and do spend a great part of my day out there.
even if his testicles haven't dropped, or if just one has, he is still quite capable of impregnating a mare. it's called cryptorchidism, and while it reduces their chance of conception, it doesn't eliminate it.
I would have a vet check your mare for pregnancy. you never know, and better safe than sorry!