When I visited the tavern the barkeep told me that Sir John was there last night but said that Sir John was seen at the cave. I returned to the cave and dug a hole (I didn't ask it to do this) and then heard a noise. It was some bandits, and I talked to their leader. The leader attacked me, and I stabbed him. I searched the bandit and found a letter written in blood from someone named John. Not Sir John, the knight's son, mind you, but John a bartender at the tavern whom had not yet been mentioned. And not the barkeep I spoke to before either.
John had apparently held a grudge against me due to some past incident, and after I stabbed him he had written this note to me in my blood to be carried to me by the bandit.
When I went to the tavern to ask the barkeep about John, he told me he knew John. Then Sir John walked in to the tavern. Sir Ivan, his father, was not mentioned again.