User blog comment:JuliusJoseph/The he Story Of Rhindon. and The Knighting of The Kings/@comment-1047588-20091005201941

We're not really sure. Susan theorized that she must have left it on her horse when they were chasing the White Stag just before they went back through the wardrobe, and somehow Dr. Cornelius managed to find it 1300 Narnia-years later.