Answers for "Renaming glacial-ravine-82580 to Blog_App... ! ! Couldn't find that app."

heroku rename

heroku apps:remane --app <old-project-name> <new-project-name>

rename heroku app local

First update the name for the heroku app on the heroku dashboard (on the heroku website)
Then do this on terminal (Make sure you're in the right repository)

$ git remote rm heroku (Remove the remote from git)
$ heroku git:remote -a <new app name> (Add it back with it's new name)