It's long and tedious but have a scan through the lost section on here, on Lurcher Search too and Dog Lost as well.
It isn't uncommon for a dog to have been stolen and then dumped. Someone who may not be responsible for the state of the dog could be looking for it. Try not to limit your search to areas either as we have seen dogs missing from Yorkshire show up in Hertfordshire.
Law also requires you to report the find to the dog warden, they may also be able to match it to a missing report.
If not, you have 2 options - 1, ask the dog warden to collect the dog, it does 7 days in the 'syst