probe launched from very fast jet

[Valiant]

I built a jet that can go around 1400 m/s with a tiny probe piggybacked. engines starve around 16k and I continue to around 40k where I detach the probe, burn till apoapsis is around 73k then circularize. Then I switch back to the jet that is back down to around 45k but the pilot is gone. What happened? 

[bewing]

Have you checked if he's back in your Astronaut Complex? If he is, then I know what happened.

 

[swjr-swis]

Craft with probe cores are not automatically crewed if you don't do it explicitly before launching (or save it at least once with assigned crew).

Are you sure you actually launched it with a Kerbal inside? Or did the probe's core fly the plane instead?