Alas, dreaded returns. Someone in an inventory office or bookstore backroom somewhere has decided to return your book to the publisher.
Maybe this is because it didn't sell. Or maybe because it got damaged in shipping, or on the shelves, or in the mouth of a busy toddler. Maybe someone on a ladder dropped it from a height of some feet onto one of its corners. Maybe the diecut in the jacket ripped. Maybe it's dirty.
One way or another, it's back in the publisher's warehouse.
If it's in perfectly salable condition, then it's put back into warehouse inventory and sold again.
But maybe... maybe it's damaged.
Damaged means there's something about it that's not salable. Damaged books go to a separate section of the warehouse, awaiting sorting into hurts and refurbs.
Refurbished books are ones that have a fixable problem. The most common type of refurbishment is putting a new jacket on the book. Publishers routinely print a few hundred extra jackets for this purpose. The Hachette warehouse, for instance, refurbishes about 4 million books a year.
Hurts are not fixable. They are a loss, and go to the pulper.
When a publisher talks of having books pulped, they don't mean the books are reduced to paper pulp. (At least, not yet.) In warehouse terms, being pulped means the books are shredded in an industrial shredder and the shredded material is packed into bales and sent to a recycling mill.
It's a little dismaying to consider that the cardboard boxes your books are shipped in may have been made out of dead books.