Hi, I did the same thing. got support on the phone. i literally had them find the transaction on hash. They had the nerve to tell me i sent it with wrong tag, to an out going wallet. and that all transactions are final and they would not return it. i yelled and screamed at this guy. "you can see i made a mistake and you will not return it??? He said he did not have authority to do so, and i had to escalate the claim. i did so and never was never contacted about the matter. They are low lives at Coinbase. i proceeded to take everything out of Coinbase. I suggest only buying on coinbase and once cleared PUT on your Ledger. they use multiple wallets as incoming and out going. and customer service has no authority to move funds. Coinbase is shit and they are not concerned with customer retention. especially now. I did later find 3.75 lumens in my non custodial wallet i don't remember ever put anything in. So......??? whatever, it was not the 5 lumen i sent to wrong tag. i would call them and have all your info prepared properly. and get irate with them. i do give them kudos for having any customer service at all.
hope this helps.