Same thing for me, only I transferred from bittrex to coinbase.
There are a lot of people on coinbase right now with the same problem.
Ive tranfered many times this is the first time this has happened, i dont know if its stolen tho because if they had my private key why hasnt my account been drained? Only my incoming transaction has gone missing im confused? It is 100% the right recieve address but theres no record of it on my coinbase that is was ever sent its not even pending