So sorry to hear this and thinking of the person whose Camino was scotched completely by an erroneous assumption and a few moments of complacency.
Having just finished the French/Swiss parts of VF, the only times I was concerned about theft was when I was in the bigger cities. There is a visible and growing problem with homelessness and people who actively approach strangers in train stations, outside of grocery stores, outside of major venues like museums and churches, begging for money for food. That didn't bother me as much as watching certain young men (not sexist, that's who the culprits are in the main) hang about on the edge of city plazas - fellows who were watching people eating and drinking who might be unwary and leave a purse or pack unattended for a minute or two. I've been a victim of this one time when I was 20, at CDG Aeroport in Paris... briefcase on the floor beside me at the checkin counter. There were lots of people around and it's a busy place. Looked down two minutes later and my briefcase had vanished - with camera, notebooks, etc... No one in line had seen anything happen. Lesson learned almost 50 years ago and it sticks to this day... don't leave anything you value unattended... full stop!!
NOTE: The thieves in Paris and Rome are beyond brazen.
Anecdote: A couple of years ago, I was standing on a street corner near Pont Neuf one morning when a very well dressed Parisienne matron walked up beside me, waiting for the light to change. Her large "famous brand" handbag was sort of gapped open on the top and I could see her wallet and phone down inside. About that time, two small fellows about 10 years old walked up behind us and I sensed a potential problem. Fellow one asked the lady for money on her left side, while fellow two started to reach into her open bag, which was between us on her right side... I said politely but loudly to fellow two, "BONJOUR". Fellow two jumped about a foot in the air and they both took off running. Lady thanked me when she figured out what had almost happened to her. Complacency can be and often is costly!