I'm not convinced. Both shirts look different. Also, there is a possibility that you don't own the font and that it is available for anyone to use.. Would like to see more concrete evidence.
It's ok folks, Atlanta United reached out to me yesterday. The fact they received my designs at the creative department, started following me on twitter and reached out about an hour after I posted this, we're working on an arrangement. The designs aren't exact, but they lifted my art direction.