Perhaps you could try this. In Mac App Store, click on Account, then sign in, and "Reset all warnings for buying and download.' Then sign out and back in and try downloading again.
(Also, make sure it's the Numbers in your Applications folder that you moved to the trash, not the Numbers that you may have in an iWork '09 subfolder within Applications. You'll probably want to keep the version that's in the subfolder because it's got features that the new Numbers does not have, at least not yet. The two versions for the most part coexist happily on the Mac.)