You talk about installing the gem, and then require a plugin. Have you tried installing the version of the Thinking Sphinx plugin?
EDIT: I speak too fast, clearly. Deployment recipes are in lib/thinking_sphinx/deploy/capistrano . Try require 'thinking_sphinx/deploy/capistrano' and you should have access to deployment recipes - in a test project, I just dropped this into my Rakefile and I have access to them.
In the new project, I put the following into my Capfile:
load 'deploy' if respond_to?(:namespace)
When I do cap -T, I see capitionano think_sphinx tasks. I think I wrote above because I have the plugin installed. / I smell like myself.
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