[tylorr]

Are there any cryptographic tools that would let you prove that that specific treasure has been found and not by the original hider?

You could store a private key in the treasure and use that to verify a signature, but how do you prove that the original hider no longer has a copy of that private key?

[ip26]

I can't imagine how cryptography could hope to distinguish between a member of the public VS a member of the public who was tipped-off by the original hider.

[shemnon42]

Use a HSM like a yubikey or Google titan key to sign the message. There are modes where the key is generated on-device and not (without significant hacking) recoverable off device.

Then physically hide the key with said treasure.

[pnwhyc]

No. But one could use a smart contract to strongly disincentivize themselves from uncovering their own treasure.

E.g. Smart contract sends 20% of total treasure (in cryptocurrency) back to the hider each year until the treasure is withdrawn. Treasure can only be withdrawn by the finder address linked to the paper wallet (private key) that was hidden. When it is withdrawn, it sends the finder 15% of the remaining treasure each year, to an address of their choosing.

This way, it’s almost never worth it for the hider to uncover their own treasure

[Cthulhu_]

Not really. The closest thing, and not foolproof, is to enlist a notary; have them verify and document the contents, seal it, note the location, then do the same in reverse when it's found and unsealed. But even then you cannot guarantee the finder wasn't told where to find it.