Is it possible to find out if I do have an additional account with Faucet Hub under a different user name?
If you are asking "would faucet hub find out I am using two different accounts (to gain ref commission)?"
Then yes, if you are using the same device and internet connection, they can.
But It doesn't matter that much as your claim is based on your IP
and
ref commission can be an issue in future and the faucethub has warned about it as well.
But again ref commission is included in the total expense of a faucet and faucethub is not taking any actions about it yet.