Getting rid of item next to cooked cod then duplicating cod into said slot

Me and a friend were playing a private survival world. Within 10 minutes of each other, both of our swords were replaced by cooked cod duplicated from the neighboring slot. Personally  attacked a phantom, then my netherite sword disappeared and was replaced with cod from the neighboring slot as mentioned before. He only noticed his sword disappearing when I said something about it. However, he did notice more cod going into his inventory beforehand.

My sword was a netherite sword with Sharpness 2, and Fire Aspect 1.

His sword was a diamond sword with Sharpness 2, and Looting 2.

I don't know if you guys can get our swords back, but we think this is some type of slot glitch. For now, we will be working to get our swords back.

Thank you!