well ... they for sure should be apologizing all over the place for their screw-up instead of using this vaguely-accusatory tone,
but since it was supposed to be a fanclub-member-only sale, asking people to provide their code seems (sorry!) reasonable.
and asking you directly is probably about four years faster and miles more reliable than asking rs.com to ascertain who's a member and who isn't.
sorry you're going through this, and i hope it works out decently for everyone.
"What do you want - what?!"
- Keith