I think they DID go into circulation if the mintage figure is correct as if not you would find more in high grade ,more than we see would of been kept or put away.
If they did enter circulation then the mintage being so low ,they have been lost ,scrapped or are in collections in different grades like any other year.
30,000 is nothing and not many people even in 1860 would of even seen one ,however its a high mintage for a non circulation coin.
Possibly the 1859 die was used for the 1860 ,rather than just thrown away , just to add a few more as it was already worn (1859 ) and the bronze die being made.