Always, before disconnecting a memory card from a computer or other device, choose "Safely Remove"!
Backup memory cards, you can do specials. utilities, but it's easier to use cloud storage, or just copy the entire map to a PC.
The most important recipe for problems with the card is formatting in a digital camera, often coping better than all utilities. Or low-level formatting using SDFormatter4 ( v5.0 ) or HDD LLFT .
When temporarily “disappearing” the memory card, freezing, etc., it is recommended to thoroughly blow out the card slot, clean everything, you can even with alcohol (but very carefully) - both the contacts of the card and the contacts of the SD slot.
If you do not record new data on the card, and the old ones after deletion appear again and the formatting does not help - the card is dead and it will not be possible to restore it, even though it is read! Bury?! She does not believe!