first of all refresh. then after that check your inventory. if your inventory is full it might be placed under other items and you would have to free up space first. i heard some finding them in the bank, u'd have to move something out of the bank and check if it landed in there. then check your blacksmith for the hero name its on, because it might have ended up stuck on that hero and you have to pull it out of the inn first to unequip. if all that didnt help you need to figure out on what hero it was last and unequip all and reequip.
for future references: after you crafted any item that you have on a hero you will have to refresh your browser to prevent items of temporarily disappearing.

good luck