Something very similar happened to me at BGW earlier this year. Just before we went on the Le Scoot (log flume), I put my car key in my pocket that had a zipper. After that we rode Griffon then headed over to Apollo's Chariot where I then noticed in line that the zipper to the pocket was open and the key was long gone. Thankfully my parents were near the resort we stayed at and had a spare so they dropped it off. The next day when we went back to the park, we decided to go to lost and found just in case and amazingly they had it!
I've lost and found the same phone twice. Once at Six Flags Saint Louis and the second time at Worlds of Fun in Kansas City. Think I finally learned my lesson.