Allianz Car Insurance

[bitsnpieces]

Ok, just one simple question:

My aunty has full comprehensive, my brother uses her car, he is included in her policy

My brother turns on car, lets it warm up and quickly runs inside to grab something, comes out, car's gone

Police find it, car has been ruined by thief, and car is towed back

Allianz says they won't cover anything because it was my brother's fault for negligence or something - leavings keys in car

So they won't cover for towing costs, or any costs to repair, so I want to know, is this nornal?

Never used full comprehensive before, and don't know if this is generally the way it is, or an Allianz thing, or they just don't want to help.

Thank you