Are they allowing backpacks I have a two year old grandson that uses one for a diaper bag

We went last night, my sister and I both had backpacks, we had no problems.

I used a backpack diaper bag for my 2 kids. No one said anything.

They have the right to search.

The signs say no backpacks but my daughter went last night she has a one-year-old told them it was a diaper bag all they did was take a quick look and let her in.