Accused of stealing from a customer? need advice?

Me and my husband have had a cleaning business for four years this is the first time we've ever been accused of stealing anything and I need a little advice. My husband and I cleaned for a older lady and she called us 2 weeks later saying that her pistol was missing. I never even seen a pistol! My husband moved the pistol from on top of the dresser along with other stuff to dust and then when he put everything back on the dresser the pistol wasn't there so he assumed she had moved it because she was going through the stuff he was taking down. 2 days later a police officer wants us to come in for questioning? Do we need a lawyer? I have really bad anxiety and find it extremely difficult to talk to anyone. So I don't want the officer to yell at Me and get in my face. Can they arrest us if they have absolutely no proof? We have never and never will steal from a customer and cannot afford for this to happen to our business. Any suggestions will be great.

Thanks.