Have seen a few of the seasoned riders just pick up with one hand and relaunch.....wont happen for most of us. Next best option and i haven't had to try this (seen on you tube etc).. lay it across your knees and launch with legs kept bent till your able to hold it with one of your hands and get close enough to your mate stranded with out a board and drop it down wind of him

or some where closer than it was to start with if all goes well!
Did try hooking a board upto my safety one day and besides being a lil dangerous it acted like a bloody sea anchor..