Saved hotbar problem

I opened my minecraft world to play and the game displayed that warning screen as usual. I saved and started playing. After some time I wanted to spawn an entity and went to my saved hotbars as I had a book with all of the commands I need. And then I saw there was nothing, all my saved hotbars were erased. Thankfully I had a copy of the book in a bookshelf. I created a new world to see if it had the hotbars and nothing. I went to a snapshot before and there they were in all the worlds. Not sure what happened or how to fix it? But it only affects this version.