I've had the mixture pulled by the DZ/aircraft owner, but never the keys. If someone
did pull my keys, they would be nursing a very sore jaw about 5 minutes later, and I would refuse to ever take them up again. The guys at my DZ know this, so we're all on the same page
Back to the subject - highly unusual for a pT6 to give out without some outside influence like overtemp or overtorque or underfuelling, however poor maintennance will of course lead to failure (more often though lead to reduced performance, which leads to high temps etc...)