The tube DID NOT blow out because it was defective. Tubes do not blow until they escape from the tire through a hole or under the bead. If the tires are working ok now the problem was that the one that blew out was not mounted correctly. Putting in thorn resistant tubes will "work," because it's hard to miss an incorrect mounting and they will not blow out under all but extreme circumstances. but it's the wrong fix. If you mounted the tires you need to learn proper mounting procedure - lots of guidance online. It's best to see the process rather than just read it, but many discussions on this forum.

If the bike shop mounted the tire you might talk to them about some compensation for the problem. Either way learn to visually inspect your mounted tire to head off problems.