If the card was not taken out of the phone at all, it is possible the card is fine and the phone is just not reading it correctly.
First try restarting (power off and back on) the phone and see if will read it then. If not, then you can try removing the card and then reinserting it to see if it will be read then.
Should that not work, try connecting it to another device, computer, etc., (the card) and see if that device can read it.
If no device at all can read it, then what is on it is gone.