Yes your hotel reservation should be listed in the MDE app and also on the MDE under your plans on the Disney web site.
Often the web site and the app are out of sync. In almost all cases the web information will be the most current and hopefully most accurate data. I always suggest that you sign out of both the app and the web site and then sign in to the web site and then the app and allow up to 24 hours for the sync to complete.
Web link:
https://disneyworld.disney.go.com/plan/
In the case of the Swan / Dolphin you will need to manually link your hotel reservation if you did not book via Disney. The Swan / Dolphin information may take more than 24 hours to be reflected in the Disney reservation system before you can link the reservation in MDE via the App or the web interface.
Dave