The sticker didn't get put on the machine? If you can't boot the machine you've got a problem. Keyfinder by Magic Jellybean will recover the license numbers from a running system but I've never tried recovering it from an unbootable system.
Hmmmm . . just looked and the current version of keyfinder - it has a "Load Hive" feature that may be able to get the information from another disk mounted to a bootable system.