Sublime Text 2 stores the files in ~/Library/Application Support/Sublime Text 2/Settings, in the .sublime_session files that are located there.
The contents of those files are a large JSON blob that contains the individual tab contents. Search in the file for the file name / tab name / a key word in the document and you should be able to get what you need.
For Sublime Text 3, use the following path:
~/Library/Application Support/Sublime Text 3/Local/Session.sublime_session
Credit to: eebbesen