I was not on watch, so I cannot give an informed answer as to why certain decisions were made at that time.
I would guess that if the initial call was to a man overboard caused by the boom on a sailing vessel, then the assumption was made that the casualty may well be suffering from injuries that would require rapid transfer to medical facilities.
Also I do not know the time difference between when the casualty fell overboard and the emergency call been made.
Taking both the above factors, assuming worst case then units were required that would be able to undertake a long term search for a person in the water, and provide/transer the casualty to medical assistance asap.
A helicopter and lifeboat were sent. Both these units are ideal for the above situation. It appears that the casualty was found fairly quickly and was uninjured luckily.
I see from the lifeboat website that a crewman had to transfer to the catamaran to recover it back to shore.
When we recieve a call we have to plan for the worst case, it seems that in this case all was resolved quickly and easliy. Maybe it could have been resolved just as well by a passing rib, but if the casualty had suffered a head injury when he was knocked off his boat and was lying face down in the water, would the same passing Rib been able to respond as effictivaly. Would the same passing rib have been able to assist in the recovery of the catamaran with the remaining crew, would you have been the one to tell her that her crewmate was been rushed to A+E.
If the incident had not of been resolved so quickly I am sure a broadcast would have been made on Channel 16.
I hope nobody takes any of my above comments personnaly, I was not involved in the incident and I do not know the capability of anyone on the rib that may of been able to offer assistance.
I think the big question is not "Why didn't the coastguard make a broadcast on channel 16" but is Wny didn't the catamaran. If the remaining crew had put out a Mayday when the person weas knocked overboard then everyone near and far would have heard and could have responded. Maybe you could have recovered the man from the water before a lifeboat and helicopter were launched I do not know it is just suppersition now.
So carry a VHF always