It appears the article doesn't actually claim he found the coins, it says, "Ernesto....has found what he believes to be the stronghold containing $25,000,000 worth of coins". It's another "Dent's Run Gold" type claim. We found the place where the gold is. Oh really, then where is the gold?
stronghold
[ˈstrôNGˌhōld]
NOUN. A place that has been fortified so as to protect it against attack.
So he found a castle where he believes the loot is contained. It's not clear he actually recovered any loot. Probably tore the crap out of that castle looking for it :-)