Preserve the actual request, the employer’s response and the steps taken to obtain appropriate evidence or clarification. Describe what remains unavailable accurately.
Keep the access problem visible
Do not create a substitute statement that claims independent verification it lacks. The official process may require further information; an internal summary should be identified as such rather than presented as the requested original. Keep a short file of the attempt itself: the date of each approach, the person asked, what was requested, and the answer given, with the messages preserved rather than summarized.
That record is what allows a later explanation to be specific instead of general. Hypothetical example: a seed-testing laboratory declines to release its analytical procedures but agrees to confirm in writing which methods the applicant was accredited to run and over what period. That confirmation answers a narrower question than the original request, and it should be presented as exactly that, with a plain statement of what remains outstanding and why.
Do not blend the employer's confirmation and the applicant's own account into a single document that leaves the reader unable to tell who is saying what. Where the employer's letter contains an assertion the applicant cannot verify, say so rather than adopting it silently, and keep any attachment in the form the employer released it. Where the employer supplies an unsigned or undated letter, ask for both before it goes anywhere, since a document with no signatory and no date is difficult for anyone to rely on.