there is no logical reason for lori to be mad at rick. darryl even said that shane had to have killed randall before he led them out to the woods. so then it should be obvious to everyone that shane was lying when he said that randall escaped and that he must have had some ulterior motive and then darryl and glenn should be able to put 2 and 2 together and figure out that shane purposely split up with rick for a reason.
that building was the safehold that they were looking for i bet.
the building at the end? probably the prison