Search within Reminders on iPhone won't find items that clearly exist, whether or not they are checked off; the same search on Mac finds the item, however. I've tried unchecking the options under System Settings->Reminders->Search, rebooting my phone, then rechecking them, but the bug still reproduces. This has existed over many versions of iOS, and I'm finding it very frustrating that it continues to go unfixed.
iPhone 14 Pro Max, iOS 26
I can confirm toggling Reminders off and on works...for a while. I did this about 5-6 weeks ago (on iOS 26.1) and discovered today that I had to do it again (on iOS 26.2). Thankfully, the 'rebuild' worked again today.
Interestingly, when toggling Reminders off, I was warned some changes had not been uploaded yet and would be lost if I continued. This suggests to me there's a sync issue somewhere; however, it's not easily repeatable.
My search problem is solved for today, but the root cause remains unknown.
First install iOS 26.2 if you haven't yet done so. Next, go to Settings > [your name] iCloud, turn off Reminders, restart your iPhone and turn Reminders back on. Wait a few minutes for the search index to rebuild.
Reminders search on iPhone doesn't find existing items
