Presumably the used filesystem for the format is exFat. Do you now if this is true? Did you by any chance interupted
the reformat as soon as you discovered that you made a mistake in formatting the card.
The manual states "Since data cannot be recovered after formatting, make sure to back up necessary data in advance." https://www.panasonic.hk/usm.ashx/e/7zt1rwYXAiWEX1X3Hkyy9Oya-c1I6Tp~RB5G1h6nzkK0J5LOPzceY89CTan60f_WT_9uHtwthepX4ieljaqKF_2TQ2w4IxW20FlS_dqC9R-UEqim0k0eiNIJxDI6R7Gg/DCGH5_EN.pdf
Whether that's universaly true and due to the formatting proces as Panasonic implemented it, I don't know.