[Gameplay] An item dissapeared from my inventory

I was playing in a normal game. As you can see on the 1st screenshot http://i.imgur.com/VLR074Z.png I had a and a in my inventory, as well as other items, and the moment i farmed my 3rd ennemy jungle camp to evolve my into a the vanished from my inventory. http://i.imgur.com/JipxGMd.png

I tried to recreate this bug in a custom game but it didn't work.