Mail searching has been a problem since Monterey for me. I was hoping it would be fixed in Ventura, but not seeing much change .
For instance. If I type in $5.83 to look for an amazon charge in my iCloud accoung on my Catalina machine running Mail 13.4 it finds it, no problem. Doing the same search on Monterey or Ventura finds no results.
I'm a macadmin (for 20 years). This problem has been driving me nuts.
I decided to setup a spare mac with clean Monterey 12.6.1 and only sync iCloud.
I let it download all of my messages and it still can't find the message.
destroyed spotlight index, let it rebuild. Then rebuilt mail env indexes...
Still can't find it.
Just tried the same thing on Ventura and sad to say, not working either.
I've been keeping a mac with a copy of Catalina around just so that I can find mail! If you can't do this, you might try searching iCloud.com for your mai. Maybe it works better there.
Another suggestions would be to export their old mail to Eaglefiler where the search works.
Hopefully, the devs see this and find a fix for 13.2 or 13.3.