I actually never heard of a walmart or target employee saying something is showing up tomorrow. Usually they will only tell you if it's available or on the shelf or if they don't have it.
I work at a retail store and I should know. Yes they usually try not to say when something will be coming in, because customers would get upset if it didn't show up for some reason and then would complain about he said she said. And plus also, we're humans too, we're lazy, so pardon us for not wanting to deal with something lol.