Somehow my pocket life calendar app was deleted from my iPhone 6 with all of my appointments for the next two months. can I retrieve the app with the populated calendar?

If the app uses the calendar database the entries should still be there. Otherwise, if it maintains its own database, it should be in the most recent backup of the phone, so if you reinstall the app and then restore a (very) recent iPhone backup the app's data should be restored. Note that restoring a backup will overwrite everything on the phone, so if you don't keep daily backups this may not be a solution.