I rebuilt the search cache without deleting the index. I searched again and received three pages of results, still far below what I should expect. About five minutes later, after looking for an answer, I searched for the same term again. This time it returned the original two results. I have not tried rebuilding the search with the delete index option selected.
I believe the only search-related add-ons I have installed are Conversation Essentials, Showcase, and XenMedia Gallery.
Where should I start?