Just did the same thing, after days spent worrying that this sort of thing would happen. There needs to be a buyback npc in the tower. Other games with similar loot systems all have failsafes in place for very rare item deletion. A confirmation prompt with a unique button sequence would not be hard to implement. Worst part is, I wasnt even deleting other items. I was so excited to have an exotic item, I legitimately thought square, the primary button for practically every other function, would decode my engram .