Database migrations to heroku don't work
Ok... let's get something clear here.
Rake db:migrate doesn't migrate the data of the database. It runs all migrations (Table creations, updates, etc) so that the database structure is the same, however the data isn't! It's a fresh new database with the same structure.
What you're doing is making sure your PG database has the same structure as your sqlite3 database and it does. But if you want to pass the data from one to another It's gonna be hard i would say. You have to create a dump file from your sqlite 3 database, change it to pg and run in your heroku app.
Here is a question about it.