Absolutely, and for Bitcoin that's a big problem for a thief. But for a private currency like ZCash or Monero, nobody can tell where the coins came from. They can't prove you stole them.

E.g. with one scheme, you destroy your coins and get a proof that you destroyed them. Later you can submit your proof to the blockchain and get new coins minted for you. But it's provably impossible to for anyone to figure out which coins you destroyed.