The only thing you accomplished in that scenario is make someone concerned that you are quitting your job and that they will be down a staff member. These aren't the things we share with coworkers that we are trying to deem as trustworthy. People that I have worked with that I'm friends with don't do weird shit like this to see if I'm a liar, we already have a relationship that is founded on trust. What you accomplished there is, at best, make a coworker worried they'll be filling in your role here shortly, or at worst, having HR looking for a reason to replace you for being unreliable.

This tip does not work in real life in the way you think it does. You are describing a canary trap, and it has legitimate applications, but not for getting a lay of the land on the coworkers at your job.

This is a shit unethical tip, there is absolutely no way you successfully employ this tactic in your life without it working against you. And if you think you do, I would argue it is because you do not understand how to interact with adults, and that the people that are hypothetically betraying your trust simply do not care what you will say if they say something you didn't want shared, because they do not like you and/or value their job more than you.