No I have never had it happen with my guys to my knowledge, the reason I say not to my knowledge is because I feed in almost total darkness so I wouldn't have been able to see it. If he seems healthy though and doing everything he's supposed to I wouldn't over think it, just keep an eye on him when he's not burrowed. If he starts bleeding without eating he may have cut the inside of the mouth with the spines from the legs as mentioned, but if it stopped right after you wiped it this more then likely isn't the case. Here in Canada we get the brown crickets, the only black ones I see are the ones outside in my yard and garden. If your using the large crickets maybe try the medium size, the one thing you want to be careful with while swallowing is that when they swallow they use there eyes to help push the item down. That's why when he swallows you will notice his eyes shut and kind of push down into his head, you wouldn't want him to hurt the inside of his mouth were the eyes are because then he could get eye infections from the inside or even damage the eye. I don't think is what happened just something to think about when feeding him. This is why I feed prekilled fuzzies, I wouldn't want one to bite one of my frogs in his mouth right behind the eye. That would be a disaster, and a for sure trip to the vet.