Since I always carry this valuable stuff in a small pouch when I go outside, I've never lost my phone, keys or wallet. It would be such a mess if I lost my wallet though, I'd have to get a new ID, a new driving license, a new prepaid card and a new NHS card.
Oh and I almost lost my car keys once, I left them on a table in a tech store, luckily when I went back inside they were still there.