Radiation pavillon hollandais perte de contact avec le vendeur

Ce n'est pas obligatoire d'enregistrer son bateau aux Pays-Bas (voir plus bas).
Peut-être contacter les autorités aux Pays-Bas par email en Anglais et leur demander de vérifier si le bateau est enregistré chez eux ?

Dans le nord de l'Europe l'enregistrement d'un bateau est souvent optionnel.

www.hiswa.nl[...]tration
Register your boat

It’s not compulsory to register your boat (in the Netherlands) but certainly a smart move. Both new and pre-owned boats can be entered in the shipping register at the Cadastre.

Registering your boat offers you various benefits, including having undeniable proof of ownership. If you’re buying a registered boat you’ll have to visit a notary who is licensed to arrange a deed of delivery. HISWA-certified brokers can assist you with this process.

Within three months of registration your boat will be given a clearly visible ‘branding’ from the Cadastre. The registration number is usually carved onto steel boats while polyester boats are provided with an irremovable registration plate. Registration always includes a letter indicating the type of boat involved.

Z for seagoing vessel (zeevaart)
B for inland shipping vessel (binnenvaart)
V for fishing vessel (visserij)
Most boats are registered under category B but if you are planning to visit ports outside of the Netherlands it may be useful to categorise your boat under Z.