Heroku rake db:migrate fails, undefined method in uninstalled gem

I am trying to get my application on Heroku, but when I run heroku rake db:migrate I get the following errors. It seems like the event_calendar gem is causing the problem, but the thing is, I've uninstalled it. There is no reference to it in the gemfile, or gemfile.lock, and it doesn't show up in gem list. Trying gem list -d event_calendar just returns * LOCAL GEMS *, and as far as I can tell all files associated with event_calendar have been deleted. Why does Heroku seem to still have a problem with it?

rake aborted!
undefined method `id' for class `EventCalendar::Event'
/app/.bundle/gems/ruby/1.9.1/gems/event_calendar-0.0.2/lib/event_calendar/event.
rb:7:in `undef_method'
/app/.bundle/gems/ruby/1.9.1/gems/event_calendar-0.0.2/lib/event_calendar/event.
rb:7:in `<class:Event>'
/app/.bundle/gems/ruby/1.9.1/gems/event_calendar-0.0.2/lib/event_calendar/event.
rb:5:in `<class:EventCalendar>'
/app/.bundle/gems/ruby/1.9.1/gems/event_calendar-0.0.2/lib/event_calendar/event.
rb:1:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:239:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:239:in `block in require'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:225:in `block in load_dependency'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:596:in `new_constants_in'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:225:in `load_dependency'
/app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.0.9/lib/active_support/depende
ncies.rb:239:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/event_calendar-0.0.2/lib/event_calendar.rb:4:i
n `<top (required)>'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0开发者_StackOverflow.7/lib/bundler/runtime.rb:64:
in `require'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler/runtime.rb:64:
in `block (2 levels) in require'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler/runtime.rb:62:
in `each'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler/runtime.rb:62:
in `block in require'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler/runtime.rb:51:
in `each'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler/runtime.rb:51:
in `require'
/usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/bundler-1.0.7/lib/bundler.rb:112:in `require'
/app/config/application.rb:7:in `<top (required)>'
<internal:lib/rubygems/custom_require>:29:in `require'
<internal:lib/rubygems/custom_require>:29:in `require'
/app/Rakefile:4:in `<top (required)>'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `load'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile' 
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:1991:in `run'
/usr/ruby1.9.2/bin/rake:31:in `<main>'

So I sent out a support ticket to Heroku while I was waiting, and it turned out that the Gemfile wasn't being pushed to Heroku, there was a problem with how I was using git and it was pushing an older version. Once I properly updated my git branches and pushed to Heroku it worked.