I'm on the hunt for a seat saver and was thinking of getting a Gel Out one. Probably won't now - I slither off the side slowly due to back issues and didn't think about getting stuck! lol. My friend has a HM seat saver, I might try that a couple of times and see how I get on before forking out...
I think I would be tempted to give neutral/negative feedback as they sold you something not fit for purpose, but because you've unpicked the stitching you obviously can't get a refund etc.
If I were in your position I would find a new use for the pad (is it like a numnah?) or if unusable just...