I went out to see Will today, and something strange happened. We started off with a little ground work, we did lunging and them some disengaging the hindquarters and things like that. Anyway, I heard a funny noise - like a hiccup. It didn't have that 'hic' noise, more airy, if that makes sense. I called my friend and asked if horses could get hiccups and she told me about Thumps. I came home and have been reading about them, and it says they normally occur in very active horses and happen 40-50 times a minute. Will is definitely not active, and it only happened a few times over a period of several minutes. I normally wouldn't worry too much about it, but he's not my horse. (Owner is out of the country.) I'm going to see if he the same thing happens again tomorrow, should I be worrying this much? And is it worth a call to the vet?