Not being able to sleep, Dean had left as soon as Sam had fallen asleep to go get himself a beer and maybe play a little poker. Since his arrival back to earth, Dean was still trying to get used to the fact he was no longer in that awful place. So, he thought he at least deserved a few beers and some peace and quiet by himself.
After a few hours sitting at the bar thinking to himself about what it meant to be back, Dean wasn't sure he was ready for what "God" had in store for him. He pinches the bridge of his nose, feeling a headache coming on from all the thoughts filling his head. So, throwing some money on the table, Dean stands from the bar stool and heads back to the motel.
When the door opens, he sees Sam standing in front of Castiel, the angel that had saved him from hell. Since reuniting with Sam, Dean had yet to tell him of his rescue and that angels and all that did exist.