Yeah, I'm assuming he knew that would prevent a trace from being done, and so that is why he went off to do it. If he knew he was going to do that though, I can't believe he didn't shut the door though as someone might think it was a strange thing for him to do if they saw him leaving the house.
I can't see him really talking about anything major though; he locked himself in the bathroom initially in order to avoid having to immediately explain why he sent the poison pen letters.