To make a long story short: if you’re using Snow Leopard, you have probably noticed that you cannot find every file on disk through Spotlight search. When you do a search for preference files, library and other system files, nothing shows up in results. But don’t worry, these files have all been indexed, they are just excluded from showing up in the results.
To include aforementioned (system) files in the results:
1. Invoke a Spotlight search window (not the Spotlight menubar search), default key combo is Cmd-Alt-Space.
2. Click (+) and select “Other…”,
3. Add “System files” from the selection to the menu (checkbox) and then
4. select to include System files in the search:

Then do a search for your preference files, bundles, etc.
Cheers.
(thanks to this article from Tidbits)
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