Kmart seemed to be pretty good, when I rang around for any remaining Op/Jetfire 2-packs at the start of the year. Since the kmart near me has a toys 'manager', I'm assuming kmarts at least have dedicated people who have a better idea of what you are asking for (because they probably specifically order in the stuff themselves).
But I think if they talk to you while in the toy section, you can get them to verify words on the packaging, and mention if it is a boxed or a carded figure you are after, and/or its price. In my case, I was telling them it was a huge box with 2 figures called Optimus and Jetfire, for about $100. It took four stores, but I was able to get the person to describe details that verified that they actually had it.

Maybe it's easier for one-off items like that exclusive 2-pack though, as a general release item in a common size class might be trickier to get them to identify... especially if the toy you want is something like a Bumblebee or Optimus.