Really not an issue! Your son LOST his deer, simple as that. Private land is just that... PRIVATE.

You shouldn't EVER assume that anyone should allow you to tromp around their private property while you search for your deer.

Here in Illinois, no one can enter your property to pursue or search for wounded game, regardless of wether it's posted or not. I like it that way and for that reason our property is strictly PRIVATE! I'm not allowing anyone to cross my fence. My best advice to them is this.... you shouldn't have been hunting close enough to my property line for your deer to cross in the first place and if it did go a long ways... you're probably not going to recover it anyway.