The Mattress Store Sold mattress.. did not deliver. Have not given refund as promised. Have not responded.. store closed. Lakewood, California

The Mattress Store in Lakewood California, sold a mattress and headboard to my elderly mother. They postponed the delivery date several times over several weeks. Ultimately, they never delivered the mattress so my mother demanded a refund. They promised to send her a check, refunding the cost of the  mattress.The headboard was paid by credit card and she got a refund for that. She has not received the check for the mattress after many requests. The store is now closed. I have tried to contact the store and the company using several phone numbers and email, with no reply.