I had been attacking the treadmill in the gym strenuously enough that when I came out I was still pretty warm. So, along with my gym bag, I put my winter coat into the trunk. It wasn't until I closed the "hatch" that I realized the fob was in that coat, not my sport coat. Although the body is mostly fiberglass, evidently the trunk compartment isn't, so the radio waves didn't reach the receiver and the trunk release button wouldn't work.
After pounding my forehead a few times, I remembered that one of OnStar's features is that they can remotely unlock the doors. Fortunately, my cell phone was in my shirt pocket, not in the coat in the car, and I had previously programmed in their phone number, so I gave them a call. After a few questions to verify that I was not actually a car thief,1 they sent a signal to unlock the doors.
It was really eerie – there was no sound, but the lights blinked and I could now open the door, and from inside I could open the trunk, retrieve the fob and drive away.
Update: When I once again accidentally locked the key in the trunk, although this time in the next generation 2017 Corvette Sting Ray, I remembered reading that the trunk lid was now fiberglass, and even that one could affix an EZ-Pass transmitter underneath. This is significant for those of us who had ordered the Performance Data Recorder – basically a dash cam on steroids – that now may be blocked if the transmitter were placed in the previous location.
So I tried the trunk release button before calling OnStar, and it popped open. One less thing to worry about.
However, it's been replaced by another! To open the gas cap one no longer has to push a button inside the car, only press the back of the cap, when it will pop open – except when it doesn't!
When the electromechanical switch fails, unlike the mechanical alternatives provided for inoperative door locks, from both the inside and the outside the car, there is none!
Fortunately, one owner in desperate straits found that prying at the top and bottom of the gas cap will pop off what is just a snap-on cover, exposing the inner workings, from where the errant pin can be dislodged. I now carry a screwdriver of a size that can accomplish this, should the need arise.
1 Actually, even knowing the correct answers, a thief would only be able to gain entry – OnStar can't also remotely start the car. I queried them about this after an occasion when I hadn't noticed that a restaurant valet hadn't left the fob in car as usual, and we had stopped at a grocery store miles away on the way home. Fortunately, when Betty Lou went inside to buy a few things I kept the car running and noticed the omission before eventually turning it off.