Company I had stocks in went bankrupt but restructured

I was heavily invested in DNR when they went into Chapter 11 last year. The nullified their common stocks. (-54,000 shares) Then they replaced them with 140 warrents for the restructured DEN (DNRRW). 

 

Do I get to write off that loss? Then if I sell my warrents, then claim those as gains?

or

Do I have to sell the warrents to declare the loss?

 

Either way, I havn't gotten anything denoting the loss, it is only marked on my investment returns as a "non; reportable action"

 

How do I file that?