The problem with introducing something like that at such a late point in the show is that apparently it was an incident so "small", it never needed to come up before. They made more waves about Sam being "abandoned" at those Clown-places than this.
So if it had been a big deal to Sam, it should have come up during one of their five million wangsty talks previously. I know it didn`t because this story wasn`t even a glimmer in the writer`s eyes back then but as it stands, it looks like not only did undefined-age-Sam completely took it in stride but by the way adult-Sam was retelling his version of events, it didn`t sound like he recalled a bothersome and/or traumatic experience at all. "Yeah, you were gone. And then kinda showed up again. Weird." Maybe Bobby had two dogs.
I agree it could have been fixed (at least a little bit) with a better cover story than "lost on a hunt". To most people "lost during something dangerous" would be cause for immediate alarm.
We know John didn`t bother to be with either one of his kids during that time so nurse nookie is a good explanation. In which case, who the fuck ever let him out of hell? Seriously.
I think his ego deluded him into thinking Dean wouldn't reveal the truth about their lives and that he would never betray John.
I know he has been established as prideful but I think his paranoia and secretiveness trumped that. Not to mention, while Dean did mention that he didn`t get "bad-touched" or beat with a wire hanger, how was John to know this wasn`t a place like this? Did he scope it out? Or just not care? It could have been rape central for teenage boys for all he knew and he would have left his son there to "rot" to teach him a lesson.
It kinda seems like noone in Dean`s life cared enough to come looking.
Apparently Glass tweeted stuff like "John did the best he could" and maybe there was more to the story". Dude, you WROTE the story. If there was more to it, it should have been in the story. This "did the best he could" stuff is the same excuse that has been used on John for ages. Hey, maybe that guy who regularly beat his kid, the telekinetic special kid in Season 1, because he couldn`t get over the traumatic death of his wife did the "best he could", too. Because hey, maybe that was actually the epitome of kindness he was still capable of. Come on.
I think the John-bashing got to ludicrous degrees with the Bobby-worship as the real father (that seems like damning with faint praise to me, considering both men at the end) but what he pulled off here was both stupid and asshattish.