Your coin finding self could beat your coin hiding self by scooping up all the coins, bringing them before a judge and arbiter and saying "here it is."

In that case, lock away the coin and hide the key among thousands of identical keys. Surely a wheelbarrow full of keys would not constitute a coin.

And if identifying the locked chamber (or container, or whatever) counts as finding the coin, then lock a bunch of them after hiding the coin in a randomly selected one.