This type of situation is always in the back of my mind when you're on the brink of a real deep freeze.
Something similar happened to me once here in NJ. I was hunting on Great Bay Boulevard, which is a peninsula that sticks out into and divides Little Egg Harbor from Great Bay and is on the south end of Long Beach Island. You can find it on google earth or any other map if interested. It is a storied gunning locale and I used to hunt there a fair amount. There are various creeks in it that cross from one side to the other so you can typically access either Little Egg or Great Bay from any of them. So it had been cold in the 20's for a while but the water is open, I launch my AA Wigeon and motor out to the where one of the creeks meets Great Bay and set up there. The bay seemed pretty open although I could see ice way out when I had gone over one of the bridges on my way out to where I launched. I was after brant and black ducks that day and anything else I might see. I remember seeing someone a mile or so out on Great Bay heading out toward the fish factory (and old processing plant on an island that's a local landmark) in a sneakbox and thinking it's too cold and too big of water to cross by myself in this weather.
Anyway, I'm there are few hours and can't remember if I got anything, but I do remember that wind changed direction which I didn't think anything of other than maybe it would get the ducks moving because it has been slow. After a while I can hear this funny noise almost sounds like broken glass far away and I'm wondering what it is. A little bit later I decide it's time to go, and I notice I can see a really big sheet of ice out a few hundred yards and know it wasn't there a little bit ago, and I realize that it is being pushed by the wind and I've made a good decision to get going. So I'm out picking up the 6 decoys I had out and I look up and not only is the ice less than a hundred yards away but it is actually splashing water in front of it because it is moving so fast. I can't even get the last two decoys in and it is all around me already. I can't run the motor because the wigeon wasn't a good ice breaking boat and it was big chunks, so I'm using my push pole to kind of go with it and push pieces out of the way when I can. I'm kind of scared about losing my boat, but I can get to the marsh and could have walked in from there if I really had to, but I sure hope I don't have to because I know I may never see my boat again. I finally get to where the creek intersects with another and forms a T and the ice gets caught in an eddy there and just stops. I'm able to just get through the ice after several minutes, now I'm in open water, and everything is OK, I start my motor, go back to where I launched and am very glad to have my boat on the trailer and getting warm in my truck.
It was just one of those freak things where the wind and the tide made that ice floe move which was at least a mile wide and I don't know how big it was on the backside. I thought of Ernest Shackleton and me being in the James Caird (that's for Steve Sanford

, and I always wondered about that guy in the sneak I had seen earlier in the day and what is was like for him when he went in later.
Things like this can happen. And like noted above, the most important thing in something like this is to keep your head and stay calm and don't fight it, figure a way to work with it and extricate yourself.
I am so glad to hear those guys are OK and that there was somebody that could help them get out, and I hope they get their boat back.