I have added full coverage unit tests, and catching a couple more edge cases. It's likely that this was only affecting users accessing the platform, as it was retrieving files using a depreciated method.
This also fixes this condition all around, where you can specify 'latest' as the version with two or three arguments, but not with four:
$ knife cookbook show corpsite-cook latest recipes default.rb
WARN: HTTP Request Returned 404 Not Found: No routes match the request: /organizations/preprod/cookbooks/corpsite-cook/latest
/usr/lib/ruby/1.8/net/http.rb:2101:in `error!': 404 "Not Found" (Net::HTTPServerException)
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/rest.rb:229:in `api_request'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/rest.rb:280:in `retriable_rest_request'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/rest.rb:210:in `api_request'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/rest.rb:110:in `get_rest'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/knife/cookbook_show.rb:60:in `run'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/knife.rb:127:in `run'
from /var/lib/gems/1.8/gems/chef-0.9.9/lib/chef/application/knife.rb:118:in `run'
from /var/lib/gems/1.8/bin/knife:19:in `load'