Disappointment

I have a treasure chest where I buy trinkets for the clas as rewards. Unfortunately, it is now put away. A student chose this squishy duck as his prize for having a reward ticket drawn this morning. The duck disappeared during lunch. Looking back, I should have just cleaned out desks myself. Hindsight is always 20-20. While I asked the kids to look for it, another teacher called and as I turned my back, it "magically" appeared on the floor under many desks. I had been watching that area to see who might have found it. Argh!!! Turning my back cost me a lot of grief. I gave the culprit ample time to fess up. Heads down...no peeking chance. Confess on a piece of paper chance. Talk to the principal chance. Talk to our second grade para chance. I took our fun activities away. Gave the guilt trip talk of how they will remember this lie for the rest of their life. Nothing!!! And yes, readers, I cried. My heart broke for a child in my room who has to lie and lie and lie and doesn't get it. Then my girls began to cry. It was a bad day. We went to gym. Went to recess. Came in...and wouldn't you know? Another person's prize from the chest came up missing. I guess they didn't learn their lesson... Any advice?