That sucks, sorry to hear it.
Yep, all fish are possible jumpers, I've never ran a tank without at least tight fitting glass tops on it. The LFS here lost a 8" black tang they had for 5 years to jumping in the middle of the night when no one was there and it was definitely not known for being a flighty fish. Sometimes this stuff just happens, who knows why, but a fish decides it's going to try to fly a little and it usually ends badly.
I wonder how many times the regal might have tried to jump before but you just never knew since it had the canopy on?