Yes! This! ^ Very wise as once you exit it will be gone. Here is the "brilliant" updated advice on "how to" on Delta.dumb

Medallion Drink Vouchers Moving to Digital
New this year: drink vouchers are now digital. Vouchers are conveniently stored under “My Wallet” in the Fly Delta app, or you can find them at delta.com, where you can print them.
To access vouchers before a flight: Open the Fly Delta app on your phone before putting it into airplane mode prior to takeoff. As long as you don’t close out of the app you will still be able to view your drink vouchers.
To access vouchers while in flight: Connect to Gogo Wi-Fi and open the Fly Delta app on your phone. You may enjoy free access to the Fly Delta app while in flight.
For more information, please visit delta.com/medallionterms.

http://www.delta.com/content/www/en_...-updates.html#


EDIT: As an FYI I just pulled one from the APP. It now went from 8 to 7 in the APP page. But, when I go to Delta.com it still shows all 8 including the one I just pulled out of the APP (but have not spent on a flight yet).