1.9.1 :014 > c = Cover.create!(title: "Some cover", state: "new", category: Category.first.id)
 => #<Cover _id: 500dfc56c4d3be50c5000003, _type: nil, created_at: 2012-07-24 01:37:27 UTC, updated_at: 2012-07-24 01:37:26 UTC, image: nil, title: "Some cover", download_count: 0, old_id: nil, tags: ["abstract"], state: "new", category: "abstract", location: "2012/07/23/0c69a210b75e012f3da20025902480d2/", slug: "some-cover", user_id: nil, approved_by_id: nil> 
1.9.1 :015 > c.save!
 => true 
1.9.1 :016 > c.errors.full_messages
 => [] 
1.9.1 :017 > c.valid?
 => true 
1.9.1 :018 > c.persisted?
 => true 
1.9.1 :019 > Cover.find(c.id)
Mongoid::Errors::DocumentNotFound: Document not found for class Cover with id(s) 500dfc56c4d3be50c5000003.
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/mongoid-2.4.12/lib/mongoid/criterion/inclusion.rb:151:in `block in execute_or_raise'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/mongoid-2.4.12/lib/mongoid/criterion/inclusion.rb:149:in `tap'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/mongoid-2.4.12/lib/mongoid/criterion/inclusion.rb:149:in `execute_or_raise'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/mongoid-2.4.12/lib/mongoid/criterion/inclusion.rb:129:in `find'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/mongoid-2.4.12/lib/mongoid/finders.rb:84:in `find'
	from (irb):19
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands/console.rb:47:in `start'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands/console.rb:8:in `start'
	from /home/rails/webapps/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.6/lib/rails/commands.rb:41:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'