The index is being rebuilt. It's taking a little longer than I remembered from last year: it might actually be tomorrow or the next day before it's done.

There's a Google custom search on the search page which is similar to site:bitcointalk.org but with some extras. The forum search is worse in some ways and better in others. If you realize that the forum search functions in terms of exact words (eg. a search of bitcoin ethereum returns posts which contain exactly the two words bitcoin and ethereum, disregarding placement and not considering related words like bitcoins), then you can use it effectively.