Would you mind posting the proof here? You should be able to add the documents you have as attachments.
Funnily enough, I nearly bought Elite: Dangerous in January. I had the exact same decision in front of me that you did: choose the benefit of playing immediately, or choose the benefit of waiting for a Steam version.
You decided to buy it when you did. You chose the benefit of immediate play. I chose the benefit of a Steam version. It's win - win! We both got exactly what we chose.

Lucky us!
It's true - I wasn't able to play in January, or February, or March. But I'm still taking responsibility for my decision. It's sad to see that you blame Frontier for
your decision.
I suggest that you boycott the game until they see sense.