Last time I had a surgery, I wrote "by participating in this surgery, all participants confirm they are covered under bcbs, and agree to waiver payment if not" right below the surgery site.
The doctor got a kick out of it, says apparently I 'got' one of his aides, who saw it, said his coverage was lapsed, and ask if a patient could do that. The doctor said he made him stand in the corner for 30 mins while they did my shoulder repair.