Contact Boat Watch Net at www.boatwatchnet.org. They will need the following information: what kind of communications gear is on board; a physical description of the boat (color of hull, hailing port or country flag, canvas color, other distinguishing characteristics); where they were headed, what their cruising plans were once they arrived; when and from what anchorage they were last reported.
The BoatWatch Net is administered by ShipCom Ltd through their public coast station WLO in Mobile Alabama. Based on the last known place and date and the intended destination and plans, they will target the inquiry to those of their members who are in the area. The website provides a form with questions including those noted above.