If you've never done this sort of thing before: there's a huge market for these "external consultants". Their unstated job (and reputations) are as whitewashing firms. You hire them to ensure there is "no evidence" of anything done wrong. The primary purpose is to create a credible defense in lawsuits but PR purposes are also common. Firms that find problems suddenly see their business dry up because most companies don't want this kind of honest evaluation (it just creates a problem and potentially exposes you to liability).
Without access to information about the firm doing the work, the report, or the underlying data it is impossible to know if a real investigation was done or not.
Without access to information about the firm doing the work, the report, or the underlying data it is impossible to know if a real investigation was done or not.