The Eagle Has Landed

John is a senior in high school who just earned his last badge to become an Eagle Scout. As a reward, the other scouts invite him to a jamboree where they plan to stay out in the woods for a week. On the first night, John learns that another scout brought a bottle of rum and says to himself, “what the heck”, I think I will have a few drinks around the fire. Unbeknownst to them, the cheerleader team had also planned to camp out nearby that evening , and the lead Eagle prompts the others to visit the cheering squad. What could possibly go wrong between such wonderful sets of kids? John is  conflicted; he dates one of the cheerleaders and ultimately wants to “tie a knot” with her, but not in his current condition.  He is now mildly inebriated and reeking of rum – his girlfriend is a card-carrying member of the teetotalers club. He does rush to his tent to brush his teeth, but realizes he forgot his toothpaste. Again, the head Eagle scout councils improvisation, ”chew on a splinter of walnut tree ”, and John complies. Unfortunately, while chewing the Oak, he feels a splinter penetrate his “lips/gums” followed by unbearable pain. The excursion to visit the cheerleaders is immediately curtailed and instead John is driven back to the ED. Examination reveals the splinter stuck in his oral vestibule and there is clear swelling on the side of the face where the splinter penetrated. His vestibule on that side of the oral cavity is dry to the touch. Where is it likely that John injured his vestibule?

Where did the splinter likely lodge in the vestibule?