I use a "Travel ideas" tag on emails from cruise lines if they suggest a specific place, time and cost to travel somewhere. Those words aren't in the email. The criteria that qualify the email for the tag are easy to check in a scan of the message but I don't know how I'd grep for them.

I still do searches but for other reasons.

If you wrote a note about a neutrino-hunting instrument at the South Pole, how many searches would it take you to find it later? What about a science station at McMurdo, which is in Antarctica but not at the South Pole?

You could allow yourself to have or not have a line of free association, whose only purpose was to match future searches that would otherwise miss because of how the content was phrased.