Each Federal Dept. has an Office of Inspector General
(OIG) that conduct internal investigations of allegations of criminal, civil and regulatory violations within the Department. They also conduct external investigations of, for example, contractors who deal with the Department for any alleged violations. The OIGs are autonomous and, by law, cannot be influenced by higher-ups within the Dept. nor by anyone outside of the Dept. within the Executive or Legislative Branches. (At least they’re not supposed to be)
So McKaskill’s request for HHS to conduct an investigation is SOP.
Somebody told me there's no tooth fairy, either, but I distinctly remember finding a quarter under my pillow the next morning.