Just checked around, and Mom still had a receipt from that used bookstore, with the exact address. 6112 Quince at Ridgway. It was located at the corner of Quince Rd and Ridgeway in the Balmoral Center. 38119 is the zip code.

I've been looking up flood maps to make sure the person that confirmed it for us was right, since more than one bookstore has the name Book Traders.

Since it wasn't the one near some railroad tracks (that may have been a different Book Rack--that one was definitely in a flood prone spot) there's a small chance Book Traders might not be the one underwater. I'm trying to find out, though.