Different systems are secure against different threats. Sticky notes are secure against people who can't get physical access to their location.
The question in this case is what attacks this experiment is secure against.
I've taken the sticky note down. It had the word "contrite"
There were plenty of exploits you could have done, without having local access to my machine. Just one example- If you view my profile, you can determine the company I work for. Use linked/etc to message someone there, and offer to split my generous reward with them, if they tell you the word.
Just because no one took me up on my offer doesn't mean my sticky-note was secure.
Yes, of course it was a silly "contest", but that's the point - Contests like this don't prove anything at all about how strong or weak your solution is.
Where are these people that are actually suggesting plausible attacks rather than just mocking the idea of a contest? I don't see them.
Those are creative solutions to your contest. I should have been cleverer.