"It illegal to use a detection device to search for archaeological objects anywhere within the State or its territorial seas; without the prior written consent of the Minister for Culture, Heritage and the Gaeltacht"
That, to me, implies there's a lot of unfound treasures over there... and/or a lot of illegal searching. Assuming there's interest outside of archeological value, of course.
Some good Samaritans sometimes send in Ireland's priceless heritage to the national museum. But of course they're not going to reveal who they are, or where they found it. They don't want to go to prison. So I guess we'll never know.