Lost Serial Numbers

I've paid for Homeworld 2 three times.

Each time, I've lost the installation media, or the manual (with the printed serial key).

Wanting to fire it up again, I found the CD, but not the serial key. Bummer. Is the only alternative to search for a crack, or someone else's serial?

I think this is the reason that platforms like Steam or Impulse are so great. You never lose your games, unless the provider goes bust, of course.