That risk is there regardless of what they steal. The kind of thieves who break into cars are low-effort-random-reward. They have neither the patience nor the skill nor the resources for the kind of planning you're referring to. Yes, the bag didn't contain much valuable. A different bag might have. Had the thief known that for a fact beforehand they probably wouldn't have bothered.

Outside nwallin's car: no valuables

Inside nwallin's car: maybe valuables?