I should add I tried mycelium with no luck ,if I have seed does that not mean its in cold storage and not on an exchange ?
I'm not sure if any exchanges use mnemonic phrases, however it may be the case. There was a number of exchanges around a few years ago which aren't around anymore. First take a look at the desktop options, and then if that doesn't yield any fruit we can take a look at some of the exchanges that were around back then, and still are.