Nope, you can't unlock that card on Trauma. This problem only shows up in the Black Edition - originally, Trauma difficulty was locked until you got all 23 other cards (one of which could only be obtained on Nightmare level). Black Edition starts with Trauma unlocked, so you can get yourself in this fix.You can keep your cards and gold when you re-sign the pact, but you'll have to replay in Nightmare to get all the cards.

You will also find that Chapter 5 is unavailable on Trauma. There is a storyline reason for this, and for why it was locked originally. This thread explains why, but it's a bit of a spoiler:
http://www.gog.com/en/forum/painkiller_black_edition/5th_chapter_doesnt_open

There is also apparently an exploit that will let you get all the cards by using BooH - apparently if you start a BooH game then start the normal one, you will get all the cards except the final (Trauma only) card [chapter 4 level 4]. That is not what you're aiming for though . . . there is a patch that will let you play Chapter 5 in Trauma (see the thread above), and there may be an exploit to grant you that single card, but you can't do it in normal play.

thanks for the through explanation. I actually beat the game before on trauma. Now it actually makes sense because I remember I went nightmare>trauma, and on black edition it was available immediately. I guess I just start with the expansion because I don't remember if I beat that one.