The question is a spoiler for the season so I'll put it behind a cut/collapse/whatever.
At the end, Sam says he's been straight with Dean (sure you're straight, sugar :)
"I told you from the jump where I was coming from, why I didn't look for you."
Um, he did? I remember him saying he stopped hunting because hunting killed his whole family, and because he had something with Amelia he'd never had, and that he didn't know what happened to Dean, but those aren't really ANSWERS to why he didn't look, right?
What Dean said, "You left me to rot for a girl" is true. I don't LIKE not liking Sam's character. I don't like what the writers are doing to him. Because he did leave Dean to rot for a girl, and not even a cool one like Jessica.
[Oh, btw, awesome wife, shacking up with the handyman a few months after burying the husband she's been with "forever." No, I'm not liking Amelia one bit.]
So why do YOU think Sam didn't look for Dean? Because I'm not buying he didn't have a clue about Purgatory.
St00pid writers. Give me my sympathetic Sammy back!