many were, but they've been identified by their family/neighbours etc. by their clothing, raided, and stolen goods found. remember that almost all the stock taken was for resale, so still in its packaging with security tags etc. these are not master criminals ...
Rioters/looters in general aren't usually the smartest breed of human, a few in past incidents have been caught well afterwards because they registered the waranty or other such idiotic things with merchandise that can be tracked via serial numbers.