There are examples of lost metals in real life. Damascus/wootz steel (the actual historical metal, not the pattern welding technique often marketed as Damascus steel) was produced for multiple millennia and was prized 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 most of its qualities, but the exact technique and circumstances behind it remain lost to time even though it only stopped being produced a mere century ago.