Dear Mary: Should I tell my boss I swiped his champagne?

Q. I have got myself in a pickle. My boss was given a bottle of Louis Roederer Cristal by a client. It came in a very smart presentation box. I thought it would be funny to open it and replace the champagne with a bottle of fizzy water. My boss duly took it home and I waited several days, expecting him to come in one morning laughing and saying: ‘Where is it?’ Alas, silence. So in passing I nudged him with a grin on my face and said: ‘How was the champagne?’ He then told me he had fallen out with a childhood friend and they had not spoken since Christmas, so he had wrapped the box and sent it to the friend – and the friend thought it was a snide prank. I have not had the guts to come clean, and the champagne remains in my desk drawer.