Did the Hyperscore actually work?

Solution 1:

Doubtful.

"It's not yet in the shops, but we've 25 to give away this week..."

source

The peripheral was intended for release in October 1995 for £29.99, but was cancelled. –segaretro.org/Hyperscore

This explains how you had one and why they don't work. I'd bet the independent seller wasn't supposed to be 'selling' you one. It would seem that marketing was way ahead of the rest of the team on this.

GamesMaster TV Series Retrospective, Part 5 (transcript) manic-expression.com:

News: The Hyper Score helps SNES and Mega Drive owners save their high scores, and Earthworm Jim gets his very own Saturday morning cartoon show