Once. Original edition, some 20-25 years ago.
I remember next to nothing about my character or the session, other than the ending. The party was fooling around with some kind of magi-tech in a vine-strewn ruin out in the jungle. As the newest player at the table, I was "volunteered" to test out the device. One blinding flash of light later and I was... gone.
The GM was pretty non-specific about what happened, and was trying to coax the others into further experimentation with the device. They shrugged, went something like "Oh well... it was only a new character. Barely one step up from an NPC. You can just make another one next week." The GM seemed slightly frustrated, but said "Fine"... and called the session.
The following week, I played D&D with a different group of friends. So that's my Tekumel experience.