[TzAkS.]

Not sure if is working,not tested but try it.

pawn Code:

if (IsPlayerNPC(playerid))
{
        new npcname[MAX_PLAYER_NAME]; 
        GetPlayerName(playerid, npcname, sizeof(npcname));
        if(!strcmp(npcname, "Name", true))// Your npc name here
        {
                ConnectNPC("NPC","NPC");//conect the npc founded with "Name"
        }
        if(!strcmp(npcname, "Name2", true))// Your second npc here
        {
        // codes
        }
}

Put it to OnPlayerDisconect so will be called just if the npc leaves the game.