Missing Something?

Madeline lost something on her walk this morning. For those of you who know her well, you probably know what it is, but I'll give you some hints.

Hint #1: And no, we didn't lose Bond. :)



Hint #2: A closer look.

Hint #3:



Do you see what's missing?

 And no, I didn't know it was missing until we were home. So we had to backtrack through our neighborhood to find her sock! Fortunately, I haven't found any tire marks on it!