One of the problems that the Z has, due to it's body shape and specifically it's rear end, is that it generates a strong vortex of turbulent air behind the rear end. It's this vortex that causes the smell of gas within the passenger compartment, since the air can be forced back into the cabin through the tail-lights, the hatch and any other opening back there. That's the reason they discontinued the hatch vents from 70 to 71.
At 110 mph, it is conceivable that you actually generated enough upward wind pressure at the hatch to actually lift it up, and sure enough you encountered that. In order to make sure this doesn't happen again, you need to check the latch adjustment to make sure that it is in fact closing completely and not just to the safety latch position which might be what happened to you.
The Safety latch on the hood is obvious, it is that handle we have to press in order to get the hood released to open AFTER we've released the hood latch. On the hatch, the mechanism throws part way, then finishes it's travel and latches a second time. This is similar to the latch on your doors. There is a preliminary latch point, followed by the final cam action that closes the door tight. To check that you are closing properly, close the latch in a normal manner, then pull up on it. If there is some play upward, then you either did not latch completely or you are out of alignment. For the first, you need to raise the latch strike and for the second, lower it.
FWIW