So many parents have experienced the horror of a small child leaving their side and getting lost in a very big store. There are parents who purchase a harness and a sort of leash for their child to prevent the problem. Then there are those who think, "I'm not going to treat my child like a dog." Still others have clever children who figure out how to remove the harness or leash and get away. This last one is one that I've seen.
I love Google because you can search for answers quickly and easily. I did a search and read a number of the answers. I found a parent who taught her child the old fashioned game of "Red Light, Green Light." I mentioned this to the mom of the child who was always running away, and she liked the idea. She taught the game to her very clever little girl. The idea, is to practice the game in several settings, starting at home, then working in a park, moving on to small stores, and working up to the larger ones. After the child learns to stop on mom saying "Red Light" you can make the game more entertaining by throwing in a different color with something else to do. For example, "Blue Light" could mean "jump up and down" or "dance." Be aware or beware of stores that have "Blue Light Specials" though. Some food stores might resort to an overhead page, "Child jumping/dancing in Aisle 5" when you yell "Blue Light. You will be able to find your child that way.
Another parent that I know professionally, has stopped her child with another solution. They have a fish tank/bowl in their home that has a high turnover in residents. Every time the little girl goes to a big department store, they make the first stop to buy a fish (for a very low price) in a plastic bag. The child has to hold the bag without running or she might drop it. This mom has never lost her child while she was holding a fish in a bag.