It sounds like you wanted a bag but some thoughts got in the way: you were worried about sounding rude, you wanted to set an example for your mom. Please correct me if I'm wrong.

Is it possible that store is giving out less bags due to environmental concerns?

I also think its ok to ask for a bag when I don't express my needs and wants, like when I just hold them in, I sometimes get that itchy "what's going on here?" Feeling that you got.