Do ghost dogs exist?

I spotted an ad in a local free paper the other day, requiring a dog walker for a 6-month old Lurcher pup. I emailed saying I had one too, and as I was already walking one, I may as well be walking two. Plus, I thought that Puffin would love to meet another pup. The lady replied saying that she usually worked from home, but that she sometimes had to work away, so just needed cover once in a while. Hmmm... sounds familiar, I thought.

So she brought her pup over the other evening - Flory. A beautiful jet black Lurcher with a smooth coat (and two white toes on each paw). We let them loose in the garden and after they spent the first 15 minutes grappling with each other (in some strange Lurcher wrestling contest), they settled down and happily chased each other around. Perfect!

Rikki said she usually paid for her other dogminder (who had since bought a business and couldn't do it anymore) but I suggested a kind of swapsie scheme instead, if she was willing to take Puffin on the days I need to work away. She agreed and we set up another 'play date' for the dogs before I look after Flory for a couple of days next week. All good.

About 10 minutes after they left, I went back out into the garden to find a small black dog sitting by the enclosure gate. Smaller than Puffin, but more sturdy. I have an area fenced off at the back (with 'That Bastard Fence' as it was referred to during construction), under RSPCA requirements that there is an enclosed space, with fencing at least 4 feet high. Not that it's made much difference to Puffin, she cleared it 2 days after being neutered (much to my horror).

Anyway, this dog was very timid and scared, she looked like she'd been sleeping rough for a couple of days and it took some gentle coaxing to get her to come to me. But she did, and submissively rolled over onto her back for a tummy tickle. All of her nipples were extended which makes me think she had recently given birth. She had no collar and no ID but a nasty deep scratch on her chest. She kept licking the roof of her mouth, so I (after securing the gate) popped back into the cottage to get her some food and water. I took about 30 seconds.

Coming back out, there was no sign of her. Puffin - swiftly shut in the cottage while this was going on - was bouncing off the walls by this point. She hates being left on her own at the best of times (she has severe abandonment issues, which I can only assume are due to whatever she went through before the RSPCA found her) and her yipping and barking was probably what scared the black dog away

Now, while Puffin can clear the fence, this mysterious little dog was too short and rotund to do likewise. So I was mystified. I spent about 20 minutes walking around the garden - there is a biggish area at the back which is overgrown with hip-high nettles and the like... but could find no sign of her. I left out the food, water, a dish of milk and something for her to sleep on and came back in.

Despite regular checks thoughout the evening, she didn't reappear and in the morning, all the food was untouched. Poor little dog. Hope she is OK, wherever she is. All very strange.