It certainly could have damaged the connection or the electronics somehow, although if your mod (battery) was fine, I'm not quite sure how, as typically if you had damaged your battery by overheating it, it wouldn't then work with a different tank. I guess that might be a possible explanation, perhaps something happened to your tank pin as it overheated. It sounds remote, but possible.
How long did you have the setup though? Unless you informed the salesfolks that this event happened, unless it was over say 12 weeks of ownership, they should have warrantied it, really, although if you did state that to them, they could very well have chalked it up to user error.
Sounds to me like something may have happened with the repeated autofiring though, so your vape store may not be being completely unfair here, in which case I'd say you could use them again without incident.
Please lock or turn off your mod during any pocket carry, no matter how brief. Also, frequently overtightening a tank on a mod can cause connection and/or other problems, so make sure you aren't screwing everything terribly tightly. If you are happy with your setup now as it is, and are looking for a backup setup (usually a useful thing to have) it might be worthwhile to check out some online vendors and see if there are some things that interest you and purchase another setup inexpensively if you can....
Best of luck, hopefully the new tank is doing the trick.
Anna