MicroSDHC not reading

I am attempting to recover some files from a Samsung 16GB microSD HC class 2 memory card.

This is my mother's card, so my understanding of the history is 2nd hand. It was previously installed in her Samsung Galaxy S3. That phone started to randomly shut down (she says w/o a precipitating event), so she brought it to get fixed and they insisted she had to upgrade. She now has a Samsung Galaxy S5. When they attempted to transfer her files over at the store, they were unable to do so, but didn't say anything about her card. Now, her card is not recognized. Other SD cards are recognized by her phone. I have tried it in her S5, my S3, and my sister's S6. I have also plugged it into a Delkin card reader (which does read SDHC cards). None of these devices even acknowledge the card exists.

I am working on a MacBook running Yosemite. I have never had an issue reading/working with cards from an Android system.

Any ideas on how to fix this? Or next steps?