Movie downloaded from iTunes store on iPad, not available on Mac
I believe you can find a Purchased section in iTunes Store, under that section, you can select to view your movies.

Also, you can log out and log back into iTunes Store (not authorize/deauthorize, log in and out). You do have to rematch iTunes Match after signing out, but it is just a single one-pass scan which will be fast.

If it not there, you may have to contact iTunes support.