Actually the same situation happened to me at 18 as well. It was my first time to 18 and I was a little bit nervous at that time. The locker boy was trying to introduce what kind of side-services came with the package I purchased (foot massage, japenese style bath services, Back Rub etc.....) I didn't pay attention whether the locker boy locked the door or not. After almost 8 hours later (I stayed over night) when I am ready to leave, I suddently found the locker door actually was open. I was shocked. So did the locker boy next to me at that time (a different guy). He was very nervous and ran to ask his manager to see this. The manager came and asked to check carefully if everything still there. I checked and luckily nothing missing. It scared the hell out of me since I was sneak out to Macau. If anything other than money was lost especially the ID etc, I will be in big trouble! I thought the managemlent may give me a discount or somesort because of this, but they didn't. Anyway, I didn't brother to ask for it too since I felt so lucky and just wanted to leave.
So be careful and always double check.
