Pokemon De-evolved Randomly

[Spencer DeRose]

i'm playing the new 1.2.2 version(it's not in the drop down list, so i'm putting it here) and i just beat Nora in the tournament at the trainer school. when i beat her, my charmander evolved into charmeleon(it was level 16.) I am now in the ancient ruins, i just beat the abyssal cult who were trying to get the riolu, and i checked my pokemon after the battle, and i noticed that my "charmeleon" was now back to a level 14 charmander. i don't know how or why.