The NTSB report states that this incident began at about 21:48, whilst flying at FL 390, and control was regained at about 21:49, at about 8000 feet. The aircraft then landed at Detroit Metropolitan Airport, Michigan, at about 22:31.
The aircraft was fitted with a Fairchild Industries Model A-100 cockpit voice recorder, which only recorded up to 30 minutes. The allegations of CVR tampering aside, the NTSB was not going to find anything useful on the CVR given that 42 minutes passed between the start of the event and the landing (quite apart from any post-landing ground manoeuvring)! It's a largely moot point.