"which brings up the other question--did tug have AIS, and did Duck have at least an AIS transponder?"
AIS might be the only thing that has a chance of helping. If, and that's a big if, there's someone paying attention to it.
I suspect AIS isn't required on the DUCs but that might be something for the USCG to look into, simply requiring it on all commercial vessels regardless of size, including all "tourist" rides.
Of course there's a requirement for keeping watch already, and we all know how well that one always works.