Rails 4 assets not loading in heroku after 'rake assets:precompile' - ruby-on-rails-4

Question

This is driving me insane! My app works properly on the local server, but when I uploaded to heroku, the css and js files didn't update. I read to precompile using rake assets:precompile to fix the issue, but then I uploaded to heroku again and now all my assets aren't loading at all! I've tried all variations of precompile, installed 12factor gem, turned some config settings from false to true, still not happening! When i look at the console, it says
[Error] ReferenceError: Can't find variable: jQuery
global code (application-38ccb09605964287831a37a0d9faf188.js, line 1)
but I do have Jquery! it works fine on local! I dunno what I'm doing wrong guys.
Gemfile
gem 'bootstrap-sass-rails'
gem 'rails_12factor', group: :production
gem 'rails', '4.0.0'
gem 'sqlite3', :group => [:development, :test]
group :production do
gem 'thin'
gem 'pg'
end
gem 'sass-rails', '~> 4.0.0'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.0.0'
gem 'jquery-rails'
gem 'jbuilder', '~> 1.2'
group :doc do
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', require: false
end
production.rb
config.cache_classes = true
config.eager_load = true
config.consider_all_requests_local = false
config.action_controller.perform_caching = true
config.serve_static_assets = true
config.assets.js_compressor = :uglifier
config.assets.compile = true
config.assets.digest = true
config.assets.version = '1.0'
config.log_level = :info
config.i18n.fallbacks = true
config.active_support.deprecation = :notify
config.log_formatter = ::Logger::Formatter.new

Answer 1

running $RAILS_ENV=production bundle exec rake assets:precompile made my heroku app work now. so i guess problem is fixed..
sorry, I don't have an explanation on why it works

Answer 2

Simply run
$ bundle exec rake assets:precompile
$ git add .
$ git commit -am "assets precompiled locally"
$ git push heroku master