Do the Rubicons still have manual shift transfer cases?
A plausible scenario I could see happening if it is electronic shift transfer case (that for some reason has a neutral setting?) Would be if they got the thing in 4low first and then pushed the switch to neutral without putting the transmission in neutral and then just assumed that the switch did its job without actually looking at the indicator lights. Still extremely stupid but I could picture an average car owner doing that.
I've gotten many phone calls from people saying "hey my truck is stuck in 4 low can you fix it?) To which I reply "yea, put the transmission in neutral and try again".