6x05 - Radio Silence
+Behind the Scenes
One of the original ideas for this episode was that Stiles would find Derek had been taken by the Wild Hunt and they would work together to get out. Derek bringing Stiles's keys with him on the return trip to Beacon Hills would be given additional significant meaning by being both Stiles's artifact and a physical representation of Derek's anchor (it was confirmed that Stiles is Derek's new anchor at the end of 3x24 - The Divine Move). As Tyler Hoechlin was unavailable due to scheduling issues, this was re-written to use Peter instead.
Source: Will Wallace's Instagram.