It's been 0 Days since the Mastodon search capability has disappointed me.
I've had "Include public posts in search results" turned on for months now, but at least on my instance, it doesn't seem to find anything more than two days old. To verify, I've tried several words that are in toots from 3 to 14 days old, and none of them hit.
#Tootfinder appears to be down at the moment, but only covers ~3 months IIRC.