It's obviously no coincidence that Sam parted from Leo and Mikaela after ROTF and Carley somehow became the latters quick replacement. Wheelie claims that Mikaela dumped Sam but (normally) when girls do that; they're already engaged with another man in their life. Could it be that Leo won Mikaelas heart over Sam? Placing bay and the hitler fiasco aside, it sort of makes sense when the two got acquainted from Alice attacking Sam. Storywise, Mikaela was already gaining interests in Leo when they got to egypt.