Well, on the legal issues, the first issue is whether the seller is private, or a trader, and that does NOT depend on whether they declared they were a trader or not, by whether they are or not, regardless of whether they said so. In fact, if they are and didn't say so (a regular event, especially with cars) that alone can be an offence.
And, obviously, if they are a trader, much more stringent rules apply.
But for the sake of argument, assume the seller genuinely is private. Then, it comes down to, basically, caveat emptor, and whether the advert was misleading. And that leads, ultimately, to a court deciding if an advert was misleafing or not. Note, the standard is that descriptions must be be false or misleading on fact. That is, exclude opinions, but then, consider both false and/or misleading.
It is possible for an advert to say "photo", but to do it in a way that is misleading, and that, ultimately, would be for a court to assess. I had a quick look at the listing when this first cropped up, and remember thinking that, on that look at least, it was badly worded and unclear. Misleading? Dunno, but it was a week or whatever ago, and I can't be bothered to go back and look again.
Suffice it to say that an unclear advert, where it certainly appears that the object of the advert was to mislead, that that could be argued, at the very least, to be clearly intended to mislead, and a court might uphold a claim on that basis.
Just stating "photo" wouldn't necessarily avoid that, though it also might. But courts aren't necessarily there to protect the stupid from themselves, either. It's not entirely clear how that listing would come out.
On "scumbag", I could have categorised the seller that way. I wouldn't distance myself from that term. I do, however, infer intent from the advert and the outcome, and I don't credit that the intent was to list, and sell, a photo. On the "looks like a duck, walks like a duck, quacks like a duck, has a bill and webbed feet" basis, I infer that something so looking like a scam was expressly intended to be a scam. Hence, scumbag seems fair enough.