As I said in my earlier post, go in and talk to them about it, and give them a chance to tell you what they will or won't do, before setting yourself by anticipating the worst.

After-thought on the possible cause of the problem, not the solution. Two stripped cranks on the same side in short order is too much of a coincidence for me to swallow, and I suspect there might be something else at work, such as a problem pedal.

The right/left threading on cranks and pedals is configured to keep a functioning ball bearing pedal tight. Unfortunately a pedal with excess bearing friction will tend to unscrew. Once it unscrews about half way out it'll tear out the rest of the way stripping the crank arm. Whenever I see a crank stripped about half way, I assume that's what happened. Don't strip a third crank, have the shop check that the pedal spins freely and the bearing is properly lubed so it'll spin freely under load.

If it turns out the pedal is the problem, it's up to you and the shop to work out who's fault it was for not having checked this last time, but at least there won't be a third time. Just in case, make it a habit to glance at your pedals once in a while to make sure they're threaded in all the way.