That sounds like some BS. I know that in WI you have by law the right to track your deer regardless of who's property it is on.
Your mistaken. If you track a wounded deer on private property without permission you will be cited for tresspassing if the landowner wishes.
Update :
I was able to talk with my neighbor and he finally agreed to let my brother retreive the deer. We found him approx. 50 yards inside my neighbors property line. I'm really happy it all worked out for the best. My brother is like a kid at Christmas now.
I'm happy to hear everything worked out well! It might be a good idea for future needs to give your neighbor a stick of sausage in thanks.