Did you check under your app store Purchases section - they should be listed there. According to this, you can download it to another Mac you own:
B. If you obtained the Apple Software preinstalled by Apple on Apple-branded hardware, in order to use
the Apple Software on more than one of the Apple-branded computers you own or control under the
Usage Rules, you must log in to the Mac App Store and associate the Apple Software with your Mac
App Store account. If you choose not to associate the preinstalled Apple Software with your Mac App
Store account, you are permitted to install, use and run one (1) copy of the Apple Software on a single
Apple-branded computer at any one time. Please also note that by choosing to associate the
preinstalled Apple Software with your Mac App Store account, you will also associate any other Apple
software applications that also came preinstalled by Apple on your Apple-branded hardware at the time
of purchase (excluding OS X, Safari, and system applications and tools).
From here:
http://images.apple.com/legal/sla/docs/Pages.pdf