When I did part-time at PetCo stocking shelves we used UHF Motorola radios but they looked more like a pager with a earpiece, only good within the store area. They did not even have an antenna in the conventional sense.
Some Walmarts use multiple frequencies at the same location and some don't.
154.57 and 154.60 are used a lot by Walmarts and several other businesses. You just have to sniff them out while close by.
If your scanner has a "service search" function you may find them that way and they're sometimes up in the 467. range as well