Permissions on raw disk not persistent

Hi, I have had an existing ASM instance running for a couple of years now, and wanted to add a raw disk to an existing disk group, so tried the following:

sqlplus / as sysasm

ALTER DISKGROUP FLASH ADD DISK '/dev/mapper/oraflash2';

Change permission on new raw disk to grid:dba, and also appended the following to my /etc/rc.local file to make permissions persistent:

/bin/chown grid:dba /dev/mapper/oraflash2

After initially attaching to new diskgroup and additional disk capacity being available, which I could confirm my using the lsdg command in ASM, the diskgroup suddenly dropped, and I cannot re-mount.