Thought you might be interested in comment 47, or you may know that already. Also in the article his father said something about stealing a phone.
I think they figured out that Rich went to an “after-hours club.” Bars in DC officially close at 2am, but sometimes on the weekend, they will close the doors and turn off the outside lights but continue drinking inside, off the books. Bartenders will invite people in that they know personally — usually other bartenders and their friends.