I'm also currently waiting for a receipt and sent a request via the web form. 16 days and counting. This is the acknowledgement email which I received:
Thank you for your request for documentation from British Airways.
Please be assured that your email is important to us and we aim to send your document within the next 28 days, however at the moment we have an unprecedented number of requests and it might take a little longer. We’re sorry for any inconvenience this may cause you.
Am I alone in thinking that 28 days as a *target* to generate a receipt (which is presumably at least a semi-automated process) is laughable? An odd definition of the word "important"... perhaps they just missed out "not"?
I didn't receive the original receipt via email, which I usually do. I've recently noticed inconsistent delivery of other comms from BA. As others have mentioned above, it seems likely that some email is going astray.