This is a lovely and funny post. I have some theories to add:

2 a. I might include break-ups that aren’t divorces and not quite so heart-wrenching but still might induce someone not to want to think about that person anymore by looking at things they gave them.

3. Book giver took back book and then gave it away. Probably in similar scenerio as above.

4. Book receiver forgot about inscription.

5. Book receiver needed $$.

I share your love of inscriptions in books and write a lot of them myself. Often times, though, I have to draw peoples’ attention to them though when I give them the book the first time. I think the real answer here is that you are a sensitive poet and a lot of people in this world are callous robots. It is hard for one to imagine the life and motives of the other.