Don C. Wiley

From 9/11 Encyclopedia:

Don Wiley was John L. Loeb Professor of Biochemistry and Biophysics at Harvard's Department of Molecular and Cellular Biology and examined dangerous viruses including AIDS, Ebola, Herpes Simplex and Influenza, and was widely known for his work in X-ray crystallography. When Wiley vanished on November 16th 2001, he was one of the most famous specialists of Structural Biology of Viruses and the Human Immune System. However the FBI didn't examine his case on possible terrorist links or a hijack. Later, the Memphis Police found Wiley's car on a bridge and came to the conclusion, that he committed suicide.

This explanation was immediately denied by his friend Philipp Marrack, a professor of immunology, supported by Wiley's friend and scientist James Davis, Wiley's brother Greg Wiley, Wiley's sister-in-law Susan Wiley, Wiley's father Bill Wiley, even the Howard Hughes Medical Institute, but this was all hidden in Memphis local newspapers only. 

Wiley planned a vacation to Iceland with his wife Katrin Valgeirsdottir and started therefore to learn icelandic language. Ms. Valgeirsdottir was at Logan International Airport in Boston on Nov. 16 2001, heading with her children to Memphis, where her husband had arranged to pick them up at the airport later that day. She received a cellphone call telling her that his rental car had been found at 4 a.m. on the Hernando DeSoto Bridge, which connects Memphis with Arkansas. The keys were still in the ignition, the gas tank was full, and the car, a white Mitsubishi Galant, was blocking truck traffic.

Don C Wiley was professor at Harvard, and conducted research at the Chevy Chase, Maryland Howard Hughes Medical Center, 
which does work for the National Institutes of Health. 

On October 1, 2001, just three days before the first reported anthrax case in Florida, the Hughes Center announced that a joint Harvard-Hughes team had identified a mouse gene that made mice resistant to anthrax bacteria. Professor Wiley had been in Memphis attending the annual meeting of the Scientific Advisory Board of St. Jude Children's Research Hospital.

On the day when he vanished, he had been at a banquet for the board at the Peabody Hotel, a short drive from the bridge, where his car was found. 
The speculations on Wiley, if he was murdered, became louder on many internet discussion groups until December 2001, when his dead body was suddenly found on December 22nd 2001.
Once again, his case was not publicly discussed in the mainstream media. More odd, his body was found, snagged on a tree, nearby a miltary hydroelectric plant in Vidalia, La., about 300 miles south of Memphis.

The Shelby County medical examiner identified the body (-> Smith, O.C). All for a sudden, the FBI started now to investigate the case. Then, almost three months later, on January 14th 2002, they changed the official explanation to an "accident", based on some obscure paint, then found on his car: "yellow paint marks on Wiley's car door indicated that he may have hit a construction sign". 
Source: http://abcnews.go.com/wire/US/ap20020114_789.html

Wiley's case contained more oddities: 
1) It took him only 40 days to "swim" in the missisippi river (with its many curves) and then already has been found. But he swam very slow, 7.5 miles a day. However due to geomorphological statistics, the Missisippi River streams with an avarage tempo of 260-280 stream miles. 
Source : http://www.vulcanmat.com/southern/web_maps/riveryards_map.htm http://www.mvr.usace.army.mil/pdw/pdf/FlowFrequency/Flow%20Frequency%20Study%20Minutes/ffs-mississippi-levees-st%20louis.pdf 
So it's plausible, that a dead body needs only 2 days from Memphis to Vidalia. 

2) Natchez Democrat reported, that his dead body was found by workers of the military Murray Hydroelectric Station. This power plant is part of the Catalyst Vidalia Corp., a subsidiary of Catalyst Energy, with the help of general partner with Dominion Capital Inc., an affiliate of Virginia Power, as a limited partner. Source: http://www.dom.com/news/archive/TempPress/fc.html

The plant was supported by the US Government, the U.S. Department of Energy (DOE), and by the Military and the US Army Corps of Engineers. http://www.mvn.usace.army.mil/pao/oldriver/hydroelectric.htm 
It was built with the help of Raytheon Engineers & Constructors, a big national weapon company.
http://www.powertel.on.ca/watson.htm