2 Samuel 9:4
And the king said unto him, Where is he? And Ziba said unto the king, Behold, he is in the house of Machir, the son of Ammiel, in Lo-debar. And the king said unto him, Where is he? And Ziba said unto the king, Behold, he is in the house of Machir, the son of Ammiel, in Lo-debar.
Mephibosheth was residing in the house of Machir in Lo-debar at the time David asked where he was. David's question located him in that place. From there David had him brought to the royal court in order to show him kindness for Jonathan's sake.