Only one thing is certain: people "forget". It's often when something disrupts the plan. At a South Island air show the fuel truck arrived and my "copilot" loosened the flush-fitting caps. The driver suddenly departed saying he would be back. The day finished and we were anxious to leave promptly. We had just enough fuel. Flew across Cook Strait for half an hour and landed after another hour and half.
At the pumps found the fuel caps hanging by the earth wire, banging on the flaps. We won't make that mistake again. Either remove the caps entirely or leave them tight: that is our rule.
Here's the thing. If we know there is a problem then smart trained people deal with it better. If we don't recognise a problem then we all stuff up equally badly.
Perhaps it takes an engine fire to reinforce exhortations: check the latches, prop the cowl open or leave it locked. If it were me now, I would tie something to the cowl, a flag or even myself. I know how easy it is to "forget" something "unforgettable".