That was one of the 3 scenarios I considered. If she was there, I thought it might explain why he would have made sure she had an atty too....NOT because I think she had anything to do with Gail disappearing, but in the event that LE attempted to question her about what led up to this argument.
Wild guess....TH drops MP off at his moms, and mom drives him home from the "airport." He is met at the door by a furious Gail who he told he wanted a separation a few days ago. She called the conference hotel and knows he didn't check in there. She met with her PI and found out more info. She tells him to go stay with his mother, he is NOT welcome in that house. Arguing ensues. MP goes to the station to get them to inform Gail that legally he has as much right to be there as she does. Mom would rather go with MP than a very angry Gail. Gail follows them up there to explain WHY she doesn't want him there. By the time the cop meets them MP is so worked up he's about to blow a gasket and the officer, out of an abundance of caution, gives Gail a number of a safe place to stay.
I'm not saying that's what happened at all. I'm just saying I can think of scenarios that aren't too crazy whereby all of these individuals would end up there.