How exactly does a paperback book get so damaged that its automatically returned to the seller by the post office?

I just received this e-mail from a place I was buying a second copy of one of my favorite books from (So that I could re-read and highlight as I wanted without feeling guilty.)
________
Dear Sara,

Your book order “Basic Instinct: The Genesis of Behavior” was damaged during delivery and returned to us.Unfortunately we do not have another copy currently. We are refunding you in full. Apologies for any inconvenience this may have caused. Please let us know if we can be of further assistance. Thank you for shopping Goodwill Easter Seals.

Sincerely, Michael
BooksForGoodwillGetJobs Customer Service Specialist
Goodwill Easter Seals
_________

Now…. how does that happen? What will they do with the book now? Should I e-mail them and say that I don’t mind it being imperfect? It really bothers me that they’re throwing away a book.