If they are on leave or in transit, they have orders, and usually a hard paper copy in hand. There's ALWAYS a phone number to the quarterdeck of their command. They call and work with the command about returning. That's the reason why when they request leave, they must provide an address or itinerary of where they will be and how to reach them in case of a recall.
Most of the bases have restricted access, and are following DoD directives which are in line with CDC and local directives. I am a retiree and went to the commissary on an AF base. A lot of ID checking, no guests allowed on base, and I didn't see anyone out and about at all. I don't think they have most bases locked down, non-essential stuff is closed.