This. When I first read OP's post, it sounded like he had a plastic grocery bag with his lunch in it -- pretty small. His clarification is that it is a canvas shopping bag -- sounds more akin to a backpack (regular sized), or even a small roller or large computer bag. So he had three items (or two personal items).

Enforcement, of course, is extremely inconsistent as to people with two personal items -- generally nonexistent in my experience. Not surprised you've been enforced 1 time out of 6. It's frustrating when the rules are not enforced consistently, but for all we know the GA's supervisor made the rule a point of emphasis that morning or even on that flight, so the GA's statement may have been literal, not hyperbole.