Because this information is critical to your security, Firefox deletes it to protect you when your password is reset to prevent other people from accessing it.
Ruma chi xa k'ayew re etamab'äl chi re ri ajikomal, Firefox nuyüj el richin yatruchajij toq nib'an ruk'ojlem ri ewan atzij richin chi majun chik winäq nrokisaj.