Can't help but had similar decades ago, coming home from work there was a ferret/polecat knocked over in the middle of the road, so stopped for a look like you do and noticed it was still breathing, took it home and it had started to come round and recovered after a while. But it was never properly tame and always nervy in general, and nervy round my runners.
I've found other ferrets and had them given over the years, all been fine.
Must of been wild or the bump had fecked it's head..