the drive should have un-instrumented as part of the decryption process. check the decryption progress with pgpwde --status --disk 0
If it shows that the drive is instrumented and there is a highwatermark value in tehre then it hasn't finished decrypting the disk. You can then run:
pgpwde --decrypt --disk 0 -p PASSPHRASE HERE
To finish decrypting the disk