That's interesting this worked - as I mentioned above, I tried looking for the actual Alchemy preset content db thinking the issue was more likely to be there, because it's *not* the ratings and tags db, which literally does only store user ratings and tags, and I didn't think that would have an affect on preset searching functionality.
I guess if that file is corrupt perhaps, then there is potential for causing weird behaviour. Or maybe a reset of that triggers Alchemy to do some kind of cleanup or re-initialisation, which could have fixed the problem.
Out of interest I had a poke around in the ratings/tags db, and it's not that interesting, and does not store the actual preset listings as I figured.
Trashing the DB file is fine BTW, you'll just lose your favourites & ratings etc, Alchemy will create a new fresh one if one isn't found. It doesn't affect the preset content.
Anyway - glad you're sorted now, and one more weird fix for a weird problem noted somewhere in the dark recesses of my brain that holds on to weird Logic quirks... 😉