I honestly can't imagine not recognising that I had the wrong dog - Bonnie is a cav, and I see loads of dogs who look very similar to her, but I'm sure I would know if I'd been given the wrong dog. I mean, there are all kinds of individual quirks such as how she sits to have her lead and harness put on, how she leaps into the back seat to be harnessed when we're going out in the car, when she barks, and at whom (birds and the poor postman ). And other little things such as where your dog sleeps, and when, and so on - wouldn't you notice if she completely changed her habits? I accept that with a self-colour dog, it's going to be harder to see immediate differences, but those dogs don't even look that alike to me.
Mind you, I don't know what I'm implying. But didn't it ever occur to either of them that they might have the wrong dog?
It's outrageous that the groomer didn't take precautions and possibly even worse that a chip was allegedly mis-read.