Not much help we can offer (only users post here).
QuickTime Player 7 was released in April, 2005 and 8 years is a long time on the software side of the Mac OS. "Pro" purchase upgrade buyers got an email with the confirmation/registration info. Maybe you still have a local copy of that email?
Apple changed their method of storing user info and purchases with the advent of the App Store but the Apple Store purchase info was left to die on the vine after 18 months.
Pony up the money again, skip a cup of Joe for a few weeks, and call things even.