Since Tahoe - previous recipients not searchable

Since my Tahoe update, I can see previous recipients via the Window menu, etc. However, people I have been emailing over and over no longer appear in the search button to the right of the main mail screen. I am using All Inboxes or All Mailboxes as search parameters. Has anyone else seen this? It has me looking up people to get emails that should be quickly accessible as soon as I start typing in their name in the To: line.