I think Martin got home. I also think that he was taunted by RACHEL to go back out and kick that cracka's arse.
This is what they were hiding.
Interesting idea ("cherchez la femme", the French cops always said), but why do you think so? Was there something in the phone-call audio that makes you think that? Or, shall we say, a "strategic gap" (as in, Rose Mary Woods and the Nixonian "18-minute gap")?