Have you ever considered that his landlord could have come into the apartment to make sure it had been cleaned up properly by the outgoing tenants (remember, he had moved in the night before his trip). If the landlord had found a poster that had fallen off the wall, he may have thought it was trash left by the other tenants and thrown it away. His landlord would not have had to break in.
I don't think it's impossible that law enforcement searched his apartment; but if they had, wouldn't his bags have been unpacked, rather than just one of them a little out of place?
But really, why doesn't he just ask his landlord or super? If the police came, they probably would have asked the landlord to let them in. I mentioned the landlord idea on the previous thread, but he never responded.