AK writes:

The tech at the shop said the brakes had worn through the rim.

Sure. My road bike rims lasted about 20000 km for this reason. My
experience is that rear rims fail earlier, even though the front wheel
carries the bulk of the braking load. The reason: More dirt.

Of course you do not want this to happen on an Alpine descent, so check
the wear regularly. If the rim flanks get noticeably concave. they are
close to being done.

Axel