The photo is from about 4 years ago. It turns out it might be under restoration somewhere, according to the text on this Flickr page:
I recovered a good few from the Tunnel hard standing after they'd been hauled out, from the mid 70s to the 90s and I certainly never clapped eyes on that one. It might well have been brought out of their collection, resprayed for the parade in 1994, then handed over to Merseyside museums after and then possibly stored by them in the open, hence the condition. So it might turn up yet.
I know the museum has this Douglas stored somewhere.