I encountered this in Canada, with an explanation given to me that there was a lawsuit at some point where an optometrist was sued after a client ordered glasses elsewhere based on the provided IPD and got glasses that caused headaches or something like that.
From Wikipedia[1]:
> In both the UK and most of Canada (excluding British Columbia[5]), the PD measurement is classed as a dispensing tool rather than a part of the actual prescription of the person whose eyes were tested, thus there is no obligation for a PD to be provided on patient request.
Are you assuming they keep records on the PD measurements of clients who didn't actually purchase glasses there? At least at the opticians I've used, I don't think they do.
From Wikipedia[1]:
> In both the UK and most of Canada (excluding British Columbia[5]), the PD measurement is classed as a dispensing tool rather than a part of the actual prescription of the person whose eyes were tested, thus there is no obligation for a PD to be provided on patient request.
[1] https://en.wikipedia.org/wiki/Pupillary_distance