I'm not sure the term "long shot" is quite accurate...

you could try a forensic audio specialist. AEA does it:

http://www.wesdooley.com/aea/forensicaudio.html

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You could load it into any DAW program and "try" normalizing it or gain changing the really quiet parts. This will of course raise the noise floor so once you boost that you'll have to filter out the noise. It may or may not work. There are phase cancelation plugins that could help with the noise floor but even I don't own them cause they're expensive and I don't really need them.

You could try bringing this to a friend with a DAW and screw around with it. But if you really need this and it's worth the money to you AEA or another forensic audio specialist is your best bet.

Good luck.

you need to chop it up, and pull your voice down, and the other guys voice up. Id use something like nuendo or cubase, where you can chop and just drag the volume up or down.
Then you need to reduce the noise floor, you need something you can listen to / preview in real time, something like cool edit or steinberg clean is pretty easy to use, and you should hear a pretty big improvement. You should be able to hear what the other guys saying, anyway.