Boarding an Aircraft Which is Not at the Gate

What prompted FlyerTalk member vsevolod4 to exclaim “I boarded a plane … which wasn’t there!”, how did vsevolod4 perform such a seemingly impossible feat, and on which airline did this occur — or not occur?!?

One has to wonder if vsevolod4 later on rented a car that was not on the lot to go to the hotel property that was not at its purported location…