One more thing;
While your insurance company might not cover based on the language of the policy, (read it for yourself and know this to be fact) your insurance company does have the fudiciary responsibility to settle the claim with those who are responsible.
My question to you is; have you filed a claim with your company or just took their word and didn't bother? If not, then file a claim. Make them put in writing that it's not covered. Then go back to them and tell them it's their duty to collect from the party involved; the consignment lot. It is their obligation to get a settlement for their policy holder regardless of the actual coverage on the item that is listed on the policy.
Sometimes all it takes is a bill from your insurance company to the consignment lot to get them to acknowledge their responsibility. Ask your agent if he'll do that for you.
Remember; take no one's word on what they say they cover or don't cover. File the claim with both; your insurance company, your homeowners policy and the consignment lot. Then be sure to get in writing their assertion that they are not responsible to cover based on specific language. They need to prove to you that specifically you are not covered, or they need to be prepared to argue their case in front of a judge.