The person would have a social security number, and face photographs in various government databases. Verification ought to be easy peasy. They do it all the ti

The person would have a social security number, and face photographs in various government databases. Verification ought to be easy peasy. They do it all the time for people abroad who lose their passports while traveling. Also, as you suggested yourself, even if he didn't have an ID on him, he would have had one at home.