item without sprite

Title pretty much says it all. I went to the Stardew Valley Fair in year 2 after having the special order board and the sprite is missing, though collision still works and I can't walk over where the board should be.

I have an inventory slot that appears empty but when I'm on it, something swings like a sword. If I try to trash it, put it in a chest or sell it to the adventurer's guild, the game crashes. If I just leave it alone, the game will crash randomly. I think I got this item from the volcano. Has...