If you had a journaling file system on the drive, such as Mac OS Extended (Journaled) (aka HFS+) or NTFS then it seems unlikely to me that a kernel panic would have "broken" the drive.
However, if you were using FAT32 on the drive then it is possible that the file system may have been corrupted when the kernel panic occurred. If you were using Windows I'd recommend running CHKDSK to check the file system and try to correct any errors in it. However, I'm not sure if the function CHKDSK performs in Windows is also provided by an OS X tool.
If you can access the drive it shouldn't hurt to try running
fsck against it.
As the comment to your question above suggests, you should first see if the drive is visible to Disk Utility. Before doing that though I would recommend completely powering everything off and then on again. Sure this may be trying to fit a Windows solution into an OS X world. Then again, it won't hurt anything and it will ensure that all the hardware is probably reset.
If you want to go a bit further to ensure your iMac hardware is reset you could also try the steps in the Apple support article below. (If it were me, I would just power off/on again first and save the SMC as more of a last resort.)
Intel-based Macs: Resetting the System Management Controller (SMC)