Absolutely, all frogs react differently to traveling to a new environment.

One question I would ask before purchasing it though, since it is relatively new, is where they got it and if they can give you any information on the breeder they received it from, if it even was a breeder. If the frog ends up being Wild Caught it could come pre-infested with parasites or diseases that could easily spread into your other frog. I would call the store and speak with the person in charge of Pet Care and ask them if they have any information on whether the frog was Captive Bred or Wild Caught. If the frog is dark green and reacting badly to the cage after being there for only a few days, chances are it wasn't bred in captivity, but this is just a guess on my part.

Another thing is see if you might be able to take a better look at the frog before purchasing it. Ask if you might be able to see it outside of the enclosure and awake, that way you can check the eyes for cloudiness and the rest of it's body for lesions, bumps, blemishes, that sort of thing.

I'm not sure if your local PetSmart would be accommodating in this way, but it really is worth asking. I bought my White's from a PetSmart down the street and one day after his fourteen day warranty expired his leg swelled up like a balloon and I found out from a vet that he had an infection that he probably caught from the conditions he was kept in at the store. Just want new members and hobbyists to know of the potential dangers when buying a frog from a chain store that seems to be in less than best condition. Mine was kept in a tiny critter keeper with nothing to climb, a cheap water bowl to sit in and a log to hide in. It was deplorable.

But anyway, just some more stuff to think about.

And yeah, a quarantine is just basic procedure. I think if you find a large critter keeper you can house the new frog in there on some paper towels for substrate and something for him/her/it to climb and hide in it would be fine for thirty days, just to weed out infection and definitely not as a long term home. Or you could use your old tank, the one you had orchid in before, since you're switching her to a new one soon, right?