The woman I spoke to at the call centre wasn't actually able to help me directly and said she needed to phone the Support Team, so put me on hold for several minutes and then came back and advised I would need to email them a copy of my receipt - nothing said about the offer not being activated, so I assume they must have checked my account and could see that it had been.
Yes, I would have thought seeing as every transaction made with an EDR card is obviously tracked so they know what/where/how many you're buying
that it would have been a simple matter for them to be able to call the transaction up on screen if I gave them the store number, receipt number and date but obviously not (although not sure why ... maybe they don't have access to price information from the transaction, only product type/quantity?).