Went to the salvage yard this morning and got the cover off by grabbing the release cable with needle nose pliers through the opening in the side of the latch, which I now realize is how I got mine off when I put the topper on. Turns out what I was pulling on before were the bungees that hold the cover down when it's folded forward. The cables on mine were broken and I rigged up a way to pull the cables manually, which is what I was thinking had been done here. These cables may or may not be intact, but as hard as I had to pull on the cable inside the latches, I doubt it would have unlocked with the key, if I'd had it. All the latches need serious lubrication. After getting the rear latches to release, I folded the cover forward, and saw what you mentioned above, but pulling on the cable the way I did worked better in this case.
The salvage yard wanted $75, which is way too much since it needs work to be usable, and it's missing parts. Could have pointed that out, plus the fact I'm pretty much the only person it's worth anything to - most of the parts that are missing are missing because I bought them last week and today - but they had other customers and I don't want it that bad.