Can they still use my music?

Are they sold independently or through a label?

Either way, they still can. Look at all the major bands out there like Evanescence, Korn, Static-X, KMFDM, etc, etc, that had a band member leave and how their album is still in print and being sold. usually there is a royalty agreement in place where the band members who contributed to that album, still get paid for album sales, even after they leave the band. so Ben Moody is still making a killing on the first Evanescence album.

How this relates to you, is I don't know if you signed a contract or anything that agrees how the band splits the revenue from the cds. If anything, you could see if they could still share a % of revenue with you.

otherwise your options would be to forget it and just move on and be happy people still listen to and buy those cds, or else go to small claims court for revenue that you should be earning on those sold album or demand an up front payment for future use of selling those albums.

You are entitled to a fair percentage of the profits seen from those CD's. Even if you left the band your work is still turning a profit. Dave Mustaine still gets checks from his old Metallica days because people still buy those albums. The same principle applies here.