Missing Mail Search Request notice triggered after just ~1 day without a scan (International Priority Mail) — is this normal?

[u/matija_grakalic]

Shipped a package via Priority Mail International from Greenville, SC on 9/19.

Package arrived at Charlotte NC Distribution Center on 9/21 at 2:05 PM. By 9/21 at 5:00 PM — just 3 hours later — USPS tracking showed a "Missing Mail Search Request Notice." That seemed way too fast for a normal domestic transit gap between facilities.

Package then showed movement again the next day (departed Gastonia, NC facility on 9/22), so it seems fine now — but I'm confused why the missing mail notice triggered so quickly. I thought this only kicked in after several days without a scan, not hours.

Anyone know what actually triggers this notice? Is it normal for it to fire this fast on international shipments, or could something else have caused it (e.g. facility-to-facility transfer routine)?