These things only get out of control if you let em.
If you're still stocking corals, you really should have some Aiptasia X (or equivalent) on hand to deal with contingencies.
Having said that, you should be able to ask THE STORE to shoot them with X for you and then hold the coral for a day so you can see if it worked. It's a reasonable request, but it's possible they might not be able to.
As long as your tank is stable and not overfed, they won't spread at a significant rate. Shoot them as soon as you get home. If you can rig a holding or QT tank up for the corals to keep them happy and do it outside the tank that's ideal, but you can do it inside the tank almost as easily. Shut off ALL your flow. Watching the Red Sea youtube video on it may help if you've never done it.
An aiptasia shouldn't stop you from getting a coral you really want, IMO. (OTOH, if it's not one you really want I doubt it's worth the effort.)