I think they’ve got this covered. ArtChain’s “Terms of Use” page says:

“ArtChain.info assumes no responsibility for any incorrect information published on the website, including any incorrect or invalid registration of any art piece… ArtChain.info is not responsible for lost private keys associated with a current owner of an art piece… ArtChain.info is not a perfect, fail-safe system for authentication”

https://artchain.info/termsofuse