You will need to check with your insurance agent but this might fall under the negligence laws of your state. If you took reasonable care to put the shopping cart in one of the collection corrals than you might not be found at fault. If instead you just placed the cart away from your car and not properly put away then fault may be found with you.

State laws differ and some laws are different if an accident occurs on in a parking lot ,especially if it is considered private property, so if your insurance agent is unable to answer the question you might try asking the insurance regulator for your state or even a lawyer.