Why would you hide an heir apparent in a “Lo Debar?” (see Lo Debar) That connection with King Saul goes back a couple of generations to the Book of Judges. In chapter 21 Israel had killed off almost all of the Tribe of Benjamin and had cursed them on top of all of that. But to find wives for the 400 Benjamites who remained they killed off everyone in a town in Gilead except for the young women. So when the newly crowned King Saul takes off and goes to the rescue of Jabesh Gilead in 1 Samuel 11 it was probably because had family there. Not only did he rescue his family but also he upped his standing in Israel at the same time. So his connection with that part of the land of Israel is family ties so the young Mephibosheth would have been safe. ( see Lo Debar – Another Look )
Lo Debar – Why Hide a Grandson There?