Weren’t some of the bills (or parts of them) recovered, leading authorities to believe that Cooper may not have survived the attempt? I vaguely recall hearing that.
That led authorities to think that he didn't survive. Why go to all that trouble and then not spend any of the money?
About $6k was found along the banks of the Columbia river. I've never heard of any more being recovered but then I suspect it would be hard to track money by the serial number, especially back then with no OCR.
“Maybe a hydrologist can use the latest technology to trace the $5,800 in ransom money found in 1980 to where Cooper landed upstream. Or maybe someone just remembers that odd uncle.”
http://www.freerepublic.com/focus/f-news/1946904/posts