Dean walked into the Bat-cave, it had been days since Cas had left them again. And, although he hated to admit it, he was actually missing him. On the table before him he noticed a shopping bag. He walked towards it, somewhat cautiously, he knew Sam hadn't put the bag there, he was out on a supply run right now. He slowly began to take things out of the bag, inside was a 'Busty Asian Beauties' magazine and a six-pack of beer. Dean shrugged and opened the magazine, a small, folded piece of paper fell out.
"Dear Dean,
I know you don't believe me, and I know you will never forgive me. But I am sorry for leaving you. I'm sorry for all the times I have left you in the past, and I am sorry for leaving you again. This time, I doubt I will ever come back. I thought I would give you something, as a thank you for everything you have done. I hope you enjoy these.
Goodbye.
From Castiel
P.S. They were out of pie."