A friend of mine accidentally transferred USDT from Binance to GDAX ... and apparently it's stuck in the Omni layer which handles these types of transactions. However GDAX is not looking for them and is not able to help retrieve or map the funds to one of it's currencies. Anyone know of a service that can retrieve the funds from the Omni Layer blockchain?
The omni layer is not a separate network or blockchain. It is simply a standardized format of transaction on the Bitcoin blockchain that uses the OP RETURN feature to move non-bitcoin assets.
In the event that your friend is able to convince GDAX to sign an Omni-format transaction using the private key for the deposit address the funds can be recovered. Otherwise there is nothing anyone can do to recover the coins. Anyone else who claims they can and asks you for private information is trying to scam you, beware.