No s197s didnt get that little feature...its an add on part only...helped a friend wire one on his gt. Sadly you're gonna need a smith. Unless you wanna drill out the trunk tumbler and then buy a new one.
Convertibles have a solid bulkhead behind the seat - can't "drop the seat" and reach in unfortunately.
Did the same thing on my car once (took off suit coat while talking on the cell phone, tossed it in the trunk and just as it latched closed remembered the keys were in the pocket!). The locksmith was able to make a key on site that opens the trunk but with no chip in it so it won't start the car. Just kept it in the center console after that.
my friend use to lock his keys in his car or trunk all the time...he eventually put a push button under the car you'd be hard pressed to find unless you knew it was there that would pop the trunk so he could bust into the car through the seats...though i know on a vert won't work the same