Running with this idea, it is at least theoretically possible since Coinbase so easily switches between Legacy and Segwit addresses, that it has derived a Segwit address from a Legacy derivation path. You could try using Ian Coleman's site (offline, of course), enter the seed phrase, scroll down to "Derivation Path" and click on "BIP141", enter m/44'/0'/0'/0 in the box titled "BIP32 Derivation Path", and select "P2WPKH" in the drop down menu titled "Script Semantics". This will generate Segwit addresses at the standard Legacy derivation path.

It would also be worth checking change addresses at that path using m/44'/0'/0'/1, and checking further accounts using m/44'/0'/1'/0 and m/44'/0'/2'/0, and checking the change addresses of those accounts too.