"Who Are You? - Oh yeah, I Already Love You"

As Saul watched David go out to fight the Philistine, he asked Abner, the commander of his army, “Abner, whose son is this young man?”  “I really don’t know,” Abner declared.  “Well, find out who he is!” the king told him.  As soon as David returned from killing Goliath, Abner brought him to Saul with the Philistine’s head still in his hand.  “Tell me about your father, young man,” Saul said.  And David replied, “His name is Jesse, and we live in Bethlehem.” [1 Samuel 17.55-58]

This above was from today's One Year Chronological Bible reading. And the following passage is from today's reading:

So David went to Saul and began serving him.  Saul loved David very much, and David became his armor bearer.  Then Saul sent word to Jesse asking, “Please let David remain in my service, for I am very pleased with him.” [1 Samuel 16.21-22]

The problem is that the latter passage occurred after the former!

So, how could Saul not know someone he was already on record for having "loved very much"?

Father, I would like to get some resolve in my head as to how Saul did not know David who had already pleased him greatly...