There are many OIGs - each Executive Department has one.
The most famous one is Horowtiz who is OIG-DOJ.
There is no such thing as THE OIG Report.
They release MANY OIG Reports on specific subjects.
What you listed is just an Investigative Summary (cover page) of a Report re: 3 FBI officials.
It's not directly mentioned by Q as a placeholder, but could fall under an existing placeholder depending upon what specific rules were broken here.