Wow, thats crazy. It's one thing when you hear stories like this when cruisers go off exploring on their own, but when it happens on a ship sponsored tour, that just shows that anything can happen. I'm glad no one was hurt. It sucks to lose watches, cameras, etc... but those can be replaced (also a good reminder to only bring what you need, limited cash, no jewelry, no passport, etc...)
I'm going on a Mexican Riviera cruise in September and heard that Mazatlan could be questionable and now this happens in PV. Hopefully things settle down by then.