You should be able to track it down with Questies, it shows the completed quests including time stamp. It should be either under Available Quests, Missing Pre Quest or Completed Quests. You could also try to search it via Questie.
Are you sure that you didn’t already pick it up (your quest log is empty/doesn’t show the quest) or that you have already done it without noticing and are on another part of the chain (like delivering it to SW).