Wanted: Experienced shield bearer

1 Samuel 17:41, 49, 55-58 - Meanwhile, the Philistine, with his shield bearer in front of him, kept coming closer to David.

Reaching into his bag and taking out a stone, he slung it and struck the Philistine in the forehead. The stone sank into his forehead, and he fell facedown on the ground.

As Saul watched David going out to meet the Philistine, he said to Abner, commander of the army, "Abner, whose son is that young man?"

Abner replied, "As surely as you live, O king, I don't know."

The king said, "Find out whose son this young man is."

As soon as David returned from killing the Philistine, Abner took him and brought him before Saul, with David still holding the Philistine's head.

"Whose son are you, young man?" Saul asked him.

David said, "I am the son of your servant Jesse of Bethlehem."

I imagine that Goliath's shield bearer was killed in the ensuing battle, but if he wasn't, I wonder what kind of employment he started seeking. He certainly wasn't much good as a shield bearer. Then again, David was maybe just that much more skilled.

Assuming again that the book of 1 Samuel is written in chronological order, I wonder why Saul did not know who David was. By this time he had already been made his harpist and armor-bearer. Perhaps David hadn't served significantly in either of those positions yet. I wonder if it was part of Saul's affliction (the evil, injurious spirit that tormented him) that he had a difficult time remembering names and faces. I recently heard that remembering faces (even those of family members) is a problem for a rather significant number of people these days.