If your in too deep then completely disregard my post, lie and deny everything.
If not:
Oh my god man, don't make a huge thing of it in your mind! Wear it next time (or something else if your excited to show him another watch). Start the conversation directly, you know this is a rep right! Laugh it off. Apologize for forgetting to tell him last time. Tell him his daughter distracted you maybe? lol. Think of something else worth mentioning that you forgot also, like you really wanted to show him where to get these amazing reps of yours. Yes?
Don't lie or compound the lie... And enjoy your watch.
I absolutely hate lying (feel like im stealing pieces of myself), I am brutally honest, but it never seems worth it. I hope one day it will be, aside from feeling honorable at the end of the day, which doesn't buy much nowadays.
good luck either way. It'd be cool to hear what happens. It's sort've like a story half read as is.