32 bit file count overflow?

My inbox, which has no expiry rules set, has gone from a 6 digit msg count encompassing dates back to 2002, had suddenly lost quite a few years worth of content, and is now showing 1522 msgs, for 91.2 megabytes.

Loosely confirmed by a du -h performed in my Mail/inbox directory, so they are truly gone.

3 or so months ago, it was showing close to 695,000 msgs, and about 12 gigabytyes. However, another folder which also has no expiry rules, is showing north of 87,000 mesgs, & 481 megs occupied.

Does anyone have a clue where they may have gone?

Cheers, Gene Heskett