The AAP released a statement saying shopping carts are unsafe for children, causing something lie 24k injuries per year. The association advises shopping online or hiring a sitter rather than taking the children with you.
I have had this happen, my son (20 months) fell out of a shopping cart in May. He was not hurt, thankfully. I felt like the bad parent of the year, until the pediatrician I ran him to said she had the same thing happen when she was shopping with her granddaughter the year before.
Now I am so crazy about making sure he doesn't fall out again, which usually means allowing him to eat as we shop. I don't like doing that either, but he stays inside. I do most of my grocery shopping alone, thankfully, but until the last month or two that was never possible.
meg