My guess is once the show ended badly Reade called a few people including his girlfriend to see what else was going on that night, and after nothing interesting was going on elsewhere, he decided to call it a night, called a cab, money, food, back to the dorms.
That makes sense to me.
I forgot to point out that in reference to the claim that Reade had his phone on auto-dial to give himself an alibi, those calls would all be timed the same amount of time apart sequentially and the duration would be the same. My understanding is that that is not the case with the times of the calls.