I cannot see any mention of a ball being present confirmed by a witness.other info says no ball - the only thing I can think is that maybe the grass on the slope was lightly frosted- that can be surprisingly slippery and not obviously icy, so if she was shooing the dog away from the water, she could have slipped, and maybe no marks because the ground was nearly frozen. I have not read if the dog was distressed when found and some dogs do not water retrieve...and the river is supposed to be deep right near that bench.
Stretch of river where Nicola Bulley vanished is 'notoriously ...
https://www.thesun.co.uk › news › dangerous-river-nicola...
1 day ago — Police fear Nicola Bulley has fallen in the River Wyre ... its deepest - close to where Nicola vanished - the river reaches a depth of 15ft.
Looking at the location of the bench, I cannot see any responsible dog owner throwing a ball from that location towards the river.
Perhaps she threw the ball in the direction of the path, Willow retrieved it and came racing back with it and dropped the ball near to the bench where it may have rolled in the direction of the river. This may have caused her to jump up drop or knock the items in a bid to reach the ball……
I would still like to understand how the Fitbit works as that was around her wrist where as the phone could be moved by anyone.