Could be if their stats server was down or if you lost connection up to the pool. Doubt it was anything to do with hacking. Best thing is to check your balance to see if it lines up with what you expect to mine per day/hour/etc
My 2nd computer, on a different address did not have this issue, therefore the post. Very strange can't figure out why.
It happened few times before, it's rare but it happens and they dont pay you when that happens.
That sucks, even with proof, can't do much?