Will the real Bob Weiner please raise your hand?
I’d say someone must secretly converted his Linux box to an Apple (without him knowing) before he left and they ran time machine, but Bob wouldn’t fall for such a horrible ploy.
Hmm, there has got to be some time manipulation or other multidimensional foolery afoot. Someone’s got some explainin’ to do.
On the other hand, if they were exact duplicates, it is likely that both Bobs would have arrived to work at exactly or nearly the same time.