Accidentally made a card untradeable

Yeah sorry to tell you wont get any help at all from EA with things like this, all mistakes are final type thing.

I mean if they really wanted to with regards to if a card has only had a cosmetic applied it should let you trade and it just removes the cosmetic, but thats not the case im affraid, UT / EA are very non UI and customer friendly :D you will learn that pretty fast, the game / UI and quality of life things could be so much more than they are but nothing really ever changes too much im affraid, took 20 years just to be able to finally see objectives while you play

If you are new to UT there are a lot more things that you can mess up like evo chains and other things, so before you put anything on cards etc be sure to check and read what it does and what it changes etc etc as they will never help / change anything back, same with SBC's make sure you always 100% check who submitting as again never get them back.