I received a very helpful email from the manager of the Deseret Book in Albuquerque today, clearing up what the status is on their supply of my book. I gather that the initial order, done by the buyer, did not include any kind of automatic re-order for when the book sold below its minimum inventory. Usually the orders do include this automatic re-order, and so the book sold out while the store had to go through the procedures to get more in. Hence the delay in having them in store. They apparently have them in now, though, as a friend just wrote on my Facebook that she bought it from them today.
If a store doesn't have a copy of a book, though, you can always order it through them. This way you only pay the cover price and not shipping. A store employee should also be able to give you an estimated arrival date for the next shipment, though you may need to ask them for it specifically.
The manager's email now has me worried that they might have overcompensated and bought way too many books and will have to return them all and hate me forever... yeah, I should probably go to bed now.