When we lived in TX, our library was constantly having AWESOME events, and tons of people came. One day, someone like "The Critter Man" came. He had a rabbit, a hedgehog, a prairie dog, lizards, etc. There was a big space on the floor for the children to sit close, and along the sides and back were chairs for parents, and he'd give a little speech on local animals, conservation, show everyone the animals and talk about them, and everyone loved it. I took my oldest son (then, he was 3 years and 2 months old) and I sat down in a chair and said "This is where I'll be. If you want to go sit up there close, you can, and when it's over, you just stand up and walk back to me. I will not move, ok? I'll be 2 chairs away from this big white pole with the fire extinguisher". He was cool with that. I had my 1 old baby with me, asleep in the travel system strollers (the kind with the infant carrier). He sat down and looked at me, and I nodded and waved, and pointed to the fire extinguisher to remind him that he could find me easily. Everything went fine. After the session was over, it was bedlam, kids all over the place, parents roaming around trying to pick out their kids, and I congratulated myself on being smart and letting him come to an immovable object instead of trying to see over everyone's heads which parent was his. I stood up and saw him walk straight to me, and all was well.
THEN: they announced "Hey, if you want to pet the animals, line up over here!" Everyone rushed over. I asked "Do you want to pet the rabbit" and he said yes! Cool. Go on, I'll be at the end of the line. (Granted, we're at this library 3 times a week so it's no big deal). He goes to the table and I watch him, and then start heading to the end of the line where he'll end up when he's finished. Stupid moms were not letting me maneuver with my stroller. I tried to be polite but then started getting nervous. Regular paths were blocked for the show, and where I could go, moms were looking at me like "Hey---I'm looking for a book and not moving". I saw Joseph go but I was far away and he couldn't hear me. I said "Please---my little boy!" at a lady and she just looked at me and planted her feet firmly, taking up the ENTIRE aisle. I panicked because my son was now out of view and I couldn't see him, and this lady wouldn't move, so I moved the stroller out of the way and actually moved to punch her (oops) but I heard someone call my name. I looked (fist in mid-air) and saw a lady I knew from Small Fry Club and she said "What's wrong?" I said "I lost Joe!" and she was like "Little Joe?" and all I could say was "MY Joe!" She nodded and said "You go to the doors. We will hit the corners and work towards you" (she was with several moms who knew me). The mom I almost punched had ducked out and was gone. I took the baby with me and left the stroller so I could maneuver better, and was jogging to the front doors when I saw him with the head librarian, at the central desk. I waved and she waved and brought him to me. All the librarians were VERY impressed and kept going on and on about how good he did, how calm he was. He just walked to the central desk and said (again, at 3 years, 2 months old): "Excuse me. My name is Jo-Jo __ and my mommy's name is A. __. I am lost." She was just standing up when we saw each other. I was proud of him but embarassed that HE had remembered what to do in that scenario, but I had not. I bragged on him and how he'd done better than me, and I learned from him, which made him pretty proud. I had to go home and lay down, I was shaking. I always thought I'd be cool, but with HUNDREDS of children roaming all over the place, and noone letting me through to get to my son, and then almost assaulting someone, I needed a truffle and a nap.
The boys are now 5 and 2, and that was the only time that's ever happened, though we go to A LOT of events. I've always told my guys that if they ever got lost, to go to "a worker" that is standing at a computer or cash register and tell them his full name, my full name, and that he's lost. And if we're at a place where it's hard to find a "worker", then to look for a mommy that has kids with her. My 2 year old has a bracelet that has my name and cell number on it (he calls it his "clock" because it looks like a watch), and my 5 year old has a Red Cross emergency fold out card in his wallet with everything from allergy info to EVERYONE'S cellphone numbers and he knows to hand that to a "worker" or whatever if he needs us. (He also has a bracelet, but only wears it at the beach, amusement parks, etc).