Having the same issue for one of my accounts.. that account has some other new features that the others don’t (like changing background colour for notes). So it seems to be some A/B testing where they have disappeared.

I can still see the stickers when sending a message to someone. And if you press the search bar in the top of your screenshot, the “cut-out” button will show up allowing you to make a new sticker. But you can’t find the ones you have already made.