Alright so support got back to me. I didn't actually receive an explanation, but it was suggested that it may have been an orphan. The funds have been credited to my exchange account and I'll try again.

Edit: All good this time, funds received. I don't mind admitting that I've no clue what an "orphan" is due to my years of rather lazily pursuing cryptos, but that I imagine this to be a problem with the exchange as opposed to a problem with the coin. I might be more inclined to appropriate blame if I better understood what just happened, but I won't be spending considerable funds via that exchange for this particular currency, because even for a tiny amount, it's hair-raising when funds disappear like that.