I traveled from Frankfurt to Japan in July for an office work. However, as my employer is based in Vienna, I always need to provide some price comparison (in form of a screenshot) for comparable flights from Vienna to the final destination. However, I can't find the screenshot anymore and I am desperately searching for a way to 'recover' prices I would have paid for this flight originally in order to get my flights reimbursed. Is there any way or service which could provide me previous date flights prices?
There are several websites which provide historical fare comparisons. However, all have gaps in their coverage, and tend to focus more heavily on US domestic flights. However, it is certainly possible one of these sites might have the record you look for.
You can find many of these sites by simply googling "historical fare comparison", but there is quite a helpful list in the answer to this Quora question.