I'm having a hard time thinking how they would do that and where. I mean Ukraine has been hitting the bridges, so that's not quite possible, Nova Khakova is under russian control and from Zaporizhzhia it's still quite a few kilometers, and all that without getting detected and slipping away again, potentially opening yourself up for capture or destruction.
Can we rule out russian incompetence and blowing up their own stuff?
Edit: ah, I see the excuse already. post below.