A 125 footer also might have draft issues. The 'Ditch' isn't necessarily the deepest piece of water around, and he might have needed to stay in the center of the channel.
Chances are he announced his intentions were announced on VHF 16 as a 'SECURITY' message. I've been up and down through there quite a few times, and it's usually busy. I usually leave my main VHF on channel 9 with a handheld on 16 just to make sure I'm not missing something.
Craig is right about the 'downstream' vessel having the right of way, too. The catch in FTL is that there are also big cross currents from all of the little canals.
BTW, as I was heading to Lauderdale Marine Center--which is nearly at I-95 on the New River, I was following a chain of motor yachts. Two of them were well over 200 feet long and had tugs bow and stern steering them. The lead boat was a 240 footer, and he was calling ahead for the bridges, letting them know there were a string of boats with a following current and needed timely openings. That was the only time I ever heard a 56' sailboat called 'small fry'. But I was. I was 'Tail-End Charlie' and took care of thanking the bridge operators as I followed the big guys through.
FWIW, the bridge operators were very courteous and prompt, and warned the 'upstream' traffic that there was a 'train' of 'downstream' boats and that we had the right of way because of marginal control.
The biggest headache there is the 17th Street Causeway Bridge, which has timed openings. The motor yachts can back & fill to maintain their positions, but most sailboats don't like to just sit still in a current, so things can get rather exciting in that area, particularly on the north side where there isn't much room.
The other headache is the junction of the New River and the ICW near the Yacht Club, particularly since there are a couple of ways of getting there, one of them down a very narrow, unmarked cut that locals use.
In any event, you need to be very alert there, and make sure you know the names of the bridges ahead of you, and not wait until you're right on top of them before you find out.
One last thought. In a right of way situation, Tonnage always wins.