Dean has died because of his Deal in order to save Sams life. You haven’t heard of Sam in that time, he could’ve done only god knows! 4 months after Deans death, he mysteriously showed up at Bobbys house, making the trio complete again.

Dean, Sam and you are sitting in the impala right now, you in the backseat and the brothers in the front. They’re arguing about the demon blood Sam got from Ruby.

Suddenly Sam said "stop the car." as he looked at Dean who resisted at first. "I’m not kidding, stop the car before I do it." this was Sams last warning and Dean finally stopped the car. Sam gets out of the car and looks over at us who also got out of the impala.

"I am not doing this to be high!” He growled looking at Dean. His older brother just stood there. "I am drinking demon blood to kill Lilith!”