When you do not have a network connection, you will still be able to purchase items using the credits you purchase from Apple (much like an iTunes Gift Card currently), except the credits would be on your iPhone locally instead of in your iTunes Store Account.
The next time you have a network connection, your local iPhone account would sync with your iTunes Store Account and the credits discrepancy would be settled.
"When a user later wishes to play back one of the media items, but the device cannot connect to a communications network to provide payment information for purchasing the media items, the electronic device can use prepaid credits that were purchased and stored by the device when a communications network was available to complete the purchase. By using prepaid credits, the media store can be assured that the user has sufficient funds for the media item purchase."
Of course the big question is, how do you buy new media items when you're not online?
The patent has that covered as well. Your device would carry a cache of media items available for purchase offline. Using the credits stored on your iPhone to ensure that you have the proper purchasing power, you are able to fully enable the cached apps. Basically, you can make a wishlist of apps and other media you may want to use later and if you choose to do so, and have the necessary credits, you would be able to purchase those items when you wish.
This wishlist could be automated using Apple's existing Genius technology:
"The recommended items can be selected based on any suitable criteria, including, for example, the media items of the user's library, recently played back media items, media item rankings, recently purchased or added media items, a preference profile defined by the user, or combinations of these."
Would you like to see an offline mode for purchasing media on your iOS device? Let me know in the comments!