Cav This is might be matter for the Gardai. This is terrible that someone would do something like this.
We can take a look at the message between you and the user and keep an eye on the account or reach out to the user.
Did you pay a deposit before seeing the dog ?
Did you get any contact information (please don’t post it) for the user name / address / anything else like vet contact.
Do you have receipt for the €400?
How did you pay the €400 cash or bank transfer (your bank might be able to reverse the transfer)
I will also reach out to you by email.