The Search by feature control on your explorer page disappears after you save keyword search settings or update the Toolkit.
Why this happens. The control hides itself while the keyword index is rebuilding, so that guests do not see a half-built search. Two things trigger a rebuild: a save under Keyword Search > Guest search > Text guests can match on, and every Toolkit update.
How long it takes. On Toolkit 3.303.1 and later, the rebuild starts immediately in the same request, so the control returns within seconds on most sites. On very large inventories, the remainder finishes over the next page loads and scheduled task runs. On earlier versions, the rebuild waits for your site’s scheduled tasks (WP-Cron), which can take up to about ten minutes on a typical host.
Finishing the rebuild right away. Open Keyword Search > Finder in the Toolkit Hub and click Rebuild, or update the Toolkit.
Checking the current state. Go to Keyword Search > Finder. The status strip reads building while the index rebuilds and returns to ready when it is done.