Artist search is broken for MP3 files in iTunes 11?

I am having a first world problem.

I am using iTunes 11.01 on 2 Macs - an old 2006 iMac running 10.7.5, and a new MacBook Pro running 10.8.2. Both exhibit the same odd behavior.

• If I add new MP3 files to iTunes (such as tracks from Amazon), artist name search may fail even though it is 100% certain that the artist is present in my library
• If I add new AAC files, buy tracks from the iTunes Store or rip a CD to AAC, everything works fine
• If I search for the album name(s), those always work correctly.

I can "fix" this by unchecking the search parameter "Search entire library", but that is not terribly satisfying. I cannot determine what is causing only certain file types to have this problem.

This is complicated by the fact that I use iTunes Match to coordinate about 20,000 tracks among my 4 devices (iMac, MacBook, iPhone, iPad).

Recipe:

1. Buy MP3 tracks from Amazon from an artist not presently in the library
2. Add them to iTunes (the Amazon downloader does this automatically)
3. Verify that the tracks play fine (they do)
4. Search for the artist name

Expected result:

Artist name is found, album is displayed

Actual result:

Nothing is found

Bizarro exception:

1. Go to another device connected to iTunes Match for this account
2. Search for the same artist as above
3. It works

Visual example:

In this example, I downloaded the new Bill Fay album from Amazon (hey, it was on sale!). As you can see, the search field is looking for "Bill Fay", and reporting that there are "No Results". But the album is plainly visible (and playing) in the album browser.

My hunch is that something about the new MP3 files causes the iTunes database to fail in some manner. The reason that other machines connected to iTunes Match work correctly is that the MP3 files are not present; only the "Matched" AAC files from the iTunes store and in iCloud.

Thoughts, y'all?