No death just went in and fetched Sams soul, putting up the wall as he inserted the soul. It wasn't a matter of time for death, just a matter of "why the heck should I?". When he decided that he wanted to get it, he just went and got it.
Let's face it, we're talking about the being that isn't all that impressed by god..he knows how to get things done!
As for the wall, we all know it is bound to get scrathed at, otherwise they wouldn't have introduced it in the first place. So now it's just a matter of waiting to see how long it takes, until Sam is once again turned into "something else"