Want to know the exact meaning of " not attended "?

a law related Question as a car was left in locked condition on day light in market. someone broke the window glass and the briefcase was stolen while the driver left the car only for 8 to 10 minutes some urgent work. the insurance co is clamming for non liability of theirs as car was not attended and refused the claim.while the car was locked & left momentary how insurance co can avoid the claim?