There are examples of lost metals in real life. Damascus/wootz steel (the actual historical alloy, not the pattern welding technique often marketed as Damascus steel) was famous for millennia for its ability to hold a sharp edge and resist shattering, before the technique to make it was lost in the early 1900s.

Modern material analysis has identified some of how and why it was so resilient and metallurgists have come up with reproductions that achieve some of its qualities, but the exact technique and circumstances behind it remain lost to time.