In the middle of the night I woke up with my teeth stuck together and in my groggy state I opened my jaw as quickly as possible. I wondered if there was damage but in the middle of the night I couldn't find any so I went back to sleep. But when I woke up I noticed there was a rough spot on my lower tooth.
My dentist got me in quickly before work today and said yes she would need to take action to fill it. She laughed at my description of the event. That my teeth had had a collision in the night. I asked if I would need to be frozen and the helper said yes. But the dentist sensed my dislike of the freezing and she said that it was shallow enough that they could try without freezing. And they did. And there was no pain. So all fixed up now.
The new backpack also seems to be pretty water resistant, so that is also good.