A missing Google review is a review that is not visible on the intended public business profile. In itself, that does not prove that Google has permanently removed the review. Google cites, among other things, checks, merged profiles and policy restrictions as possible explanations. Begin by establishing where and since when the review is missing.
According to Google on missing or delayed reviews, checks can take a few days. There is no general guarantee of restoration. Use the step-by-step plan below to separate observations from suspicions and to ask for help with a usable file.