The ath9k module couldn't be found because you, just like I and almost everyone else once did, had the assumption that the ‘rmmod’ command is a safe way to unload modules inserted with the ‘modprobe’ command.
The thing is: The ‘--remove’ option of the ‘modprobe’ command resolves module dependencies, just like a package manager. On the other hand, the ‘rmmod’ command simply removes the module, no matter if there are dependent ones loaded. Besides, I'm not sure, but perhaps the main reason for the ‘modprobe’ command to not be working when trying to reload the ath9k module is because ‘rmmod’ seems to also remove the module from the "list of loadable modules", but then again, I'm not sure as I can't find references to back this statement up. We could perhaps try inserting the module again by doing: sudo insmod "/lib/modules/$(uname --kernel-release)/kernel/drivers/net/wireless/ath/ath9k/ath9k.ko"
