CarFax only reports what is submitted to the service anyway. Mostly dealers and high-end repair shops. Joe Mechanic or Johnny Repair will usually not report anything.
My wife slid her BMW on golf course grass and bumped a stationary object. I repaired the minimum scratches and dents, straightened the fender, and painted to match. No report. Air bags didn't even release.
I know, CarFax is for maintenance, and minor to major damage... but I imagine many do not get reported. Seems to me tho', our Lance has an ID number and a Model number - but it's in storage so I can't look at it. But no wheels or engine would preclude anything reportable, I'd guess. And, it's not practical for a site like CarFax to report water damage, for example, it's not so easy to find even when we want to find it.