Item in Hotbar slot 1 turns into item in Hotbar slot 4

I was chopping trees yesterday with my enchanted diamond axe in hotbar slot 1. I noticed my hunger bar was going down so I switched to hotbar slot 4 to eat some cooked chicken. Before I finish the chicken (I was still chewing it), I quickly switched to hotbar slot 1 to pick up my axe, just to found out in one split second my axe turned into the 13 chickens in hotbar slot 4 that I was just chewing. And I was still “chewing” the 13 chickens which now were duplicated in hotbar slot 1 after the bug. I got 13 extra cooked chickens but my axe went missing forever.