open.EOS are hold in an ethereum wallet by Open Ledger.
If the current EOS token on Ethereum is in fact exchanged to the core token on the EOS blockchain, then the entity entitled to the core token is first Open Ledger. They claim that they will then replace all open.EOS with the real core tokens, but they will still be the ones holding them for you.
If you want to "own" them now, you can purchase open.EOS and withdraw them into your own ethereum wallet.