Thanks for the report! I tried reproducing the issue on my end, but I haven't been able to get it to happen yet. When it happens, does reloading the game clear the bug, or do the phantom ingots stay until you "smelt" them again? Also, if you don't mind sharing, are you playing on mobile or PC, and which browser are you using?
Really appreciate you taking the time to let me know about this, and I'm so glad you're enjoying the game!
As for hard mode, it is extremely difficult and it's meant as an extra challenge for players that have already 100%ed the game on standard difficulty. The lack of stamina recovery item (flask) and max stamina boosting footwear make it especially brutal.