What Disney usually tells the CMs is to stay with the child and look in the immediate area for the parents (who are usually frantic, crying and much more panic-y than the child

). If you don't find the parents within a reasonable amount of time (most reunions occur within five-ten minutes), then you would take the child to the baby center or Town Hall. But a usual good rule of thumb is to tell a child to look for a female CM to ask for help. Why a female? Cause women (sorry guys) are less likely to be dangerous to a child. Not a 100% certainty, but slightly safer. Also, you want the child to know what hotel you are staying in, how to get a hold of you, what your names are, etc. You could even get a Passporter pouch to put the info in. Also, please don't yell at your kid for getting lost. I used to see this all the time, and I hated it. Even though you might want to kill them for putting you through a 10 minute heart attack, be thankful that you got the little Houdini back!
Sidenote: As a kid, I never got lost at WDW. However, I would routinely get lost in grocery stores at home! Mom would tell me to put an item back, or to go get an item, and by the time I had gotten back, she'd be three aisle ahead! Think she was trying to tell me something?