After camouflaging as Renekton, Neeko's resource bar changed to fury

It happened to me once on Nexus Blitz. The bar actually showed mana, but it was white and said "% fury" after alt-clicking. Even after I became Neeko again. Moreover, mana items and manaflow band stopped working. It switched back to mana after I died. I don't know how to recreate that bug, because it only happened once.