We were able to go on a field trip to the beautiful San Diego zoo yesterday. Steve and I had our three grandchildren three and under, plus our youngest three girls. We did very well and had a great day. Steve took the first picture before we went in. He wanted some reference if anyone got lost during the day. When traveling with small children it happens. A lot. We didn't lose anyone yesterday!!
One time I lost a son there for forty-five minutes. I was a nervous wreck. He on the other hand was walking around looking at the monkeys. Another time I lost a son when we were there with elderly relatives. We had stopped and were debating if we should go on the bus tour or not. He took his time into his own hands and actually went to the bus tour spot and stood in line. Once we went to LEGOLAND and a son told the security officers he was "losed." And yet another was lost at Disneyland. Our youngest son got away from us. My husband told security our son wouldn't ask for help (he's a non-talker to strangers and pretty much to people he knows anyways) he would just walk around until found. And that's what he did.
Another strategy we have used before is placing a business card or our number in the child's pocket in case they're lost.