I think you are right, i have not seen any slime trails or any slug/snails or any other insect. I am thinking because the damage is so severe it is more than likely slug?snails.So is it slug/snail night brigade at work,gone by morning.Interesting i have 2 pots with hydrangers in and dont have any damage to them, what i find strange is ,these hydrangers have been in the garden for many years and have never been attacked like this before.I do have slug?snails in my garden and do put pellets down in the summer,but have not for the last few weeks, and thats where i have failed,but why did this attack never happen before? the only consolation is the leaves will be falling off soon. Many thanks.