My kids pretty much knew that they had to stay in the cart... it wasn't an option to ride in the basket, or walk... (until the next baby came along... 3 kids in 4 years was fun!) If they threw a fit, we left.
Hubby made the mistake of taking the 4 kids into a store just to look at softball gloves for the oldest (she was 9 at the time, the baby was 15 months old)... he didn't bother getting a cart, they were coming for just the one item. (I was on a weekend retreat with friends from a Bible Study... he had the kids for the weekend.. whew!)
They stopped at the snack bar and got a treat, then went to sporting goods... hubby put the baby down (he was walking), and helped oldest with the gloves.... he forgot all about the little one!
Pretty soon, he heard an announcement.. "Would the parents of a little boy or girl (he had curls) in red overalls please come to the snack bar?"
Our son had wandered off!
He learned a valuable lesson that day...... gotta be sure to keep the little one corralled!