The other thing I "always" do (though it's possible I might have neglected to do last time—maybe I exited my bed head first that morning, who knows?
—hence the tiny amount of seepage I experienced) is to carefully clean up the drain plug & surrounding area when I'm done. Then I start the car (still elevated), letting it run for a minute or so. Gives me a chance to check for leaks.
Rexcramer's theory sounds pretty plausible to me btw.