Hedgehogs can be surprisingly good climbers. I remember reading years ago about a hedgehog which had escaped from a brick walled shed, when it apparently could only have somehow climbed up the wall. But even so, a wheely bin sounds unlikely – being so smooth.
If the things looked like dried up slugs, is there any chance they could have been dried up slugs? I have seen dried up slugs here before, although luckily not recently, and assumed that one of my then neighbours may have been using slug killer. They could have moved a fair way from the source. I wouldn’t say hog poos looked quite like dried up slugs and if they’ve been eating a good proportion of natural diet, tend to have slightly shiny bits in them from beetle wing cases.
It might be worth you checking out what other wildlife poos look like, i.e. fox for instance. You can find some examples if you search for the Wildlife Trusts, identify poo.
Good idea to put some logs back out – it all helps.
Hope you manage to solve the mystery. Good luck.