a few other tidbits....I once had a bag where the zipper periodically opened by itself as we walked around. I nearly lost my stuff a few times, until I clipped it, then replaced it.
Over the course of many extended-family trips, we've also periodically had the misfortune of accidentally leaving our bag behind. It is easy to forget a bag when you are distracted. This is why cross body bags are helpful: they never come off in the parks. if you ever lose anything though, it is worth checking at the Lost and Found offices. There is one for each park (though eventually, I think staff said it all goes to the MK L and F), and there is one at each resort.