If that happened only one time I wouldn't see much of a problem here because it might really be just a lag. Of course if you've noticed any other suspicious avidence indicating that he could be hacking then this would make perfect sense that he might be truly a hacker. But if this is only think that happened than we can only speculate.
Maybe developers who are experienced in this sort of think and know how this server works might actually know the answer, but for now i think that no one is 100% sure if it was lags or hacks.