OK, after formatting the SD on a windows machine, it was correctly detected again. However, this also coincided with the kernel upgrade to 3.16.0-30-generic. I *think* I tried it with the new kernel and it didn't work but it's possible I'm misremembering.
In any case, my issue is resolved for now. Thank you so much for your help! I wonder if this still represents a bug somewhere if a broken SD card can not be detected.
OK, after formatting the SD on a windows machine, it was correctly detected again. However, this also coincided with the kernel upgrade to 3.16.0-30-generic. I *think* I tried it with the new kernel and it didn't work but it's possible I'm misremembering.
In any case, my issue is resolved for now. Thank you so much for your help! I wonder if this still represents a bug somewhere if a broken SD card can not be detected.