I think the problem laid with the way you told the QR check in agent that you wanted to 'claim' the miles...
In fact you should just tell them that you want to earn miles on UNITED and give them your UNITED frequent flyer number.
But if you didn't do that, then your miles will not get credited to UA. Calling QR is not the point cos you want your points to go to United and therefore United's FFP will have to process the claim - not Qatar Airways.