No It Isn't legal. Only legal If It's not posted.

Exceptions
• A person on foot may, without permission, enter land that is not
posted to retrieve a wounded animal that was lawfully shot, but
may not remain on the land after being told to leave.
• A person on foot may, without permission, enter private land
without a firearm to retrieve a hunting dog. After retrieving the
dog, the person
must immediately leave the premises. This exception
does not authorize
the taking of the wild animal.

As for the starter of this thread, you did the right thing all though I'm sure It was tough to do. If I would've been you I might of called him a few hours later and If no one answered or got back I would've made the trip over to his place In person and said a few things. Heck he could've went with you 2 to retrieve your sons deer If It would make him feel better.