When I play Minecraft and hold my bow in hand it will not show the bow. It shows all other items including sword, axe, shovel. And other items. It seems to do it sometimes and just recently started to happen on my Amazon Fire 7. It only does not show  it on Survival. But shows on creative.

It happens only sometimes and my Hide Hand option is off. 

When I change to creative on survival the bow shows again. 

It sometimes happens and sometimes does not.