Why your QR scans show as Unassigned in GA4
GA4 files traffic using a fixed list of recognised medium values, and there is no rule for a QR medium. The sessions are not lost, they are unclassified, and there are two honest ways to fix that.
Tracking
Guides on dynamic QR codes: how they work, why printed codes stop resolving, how a scan reaches the right GA4 channel, and what to check before you print.