thanks for so many guess but no one found the sliver of joey's ear between mum's elbow and knee - I hope you had fun trying you koala sleuths :)
I was asked to post the solution so here tis https://365project.org/koalagardens/365/2018-06-27
OMG !! I would never have guessed !! but it gave us a great exercise in observation skills , !! Memo - must do better next time ! Great shot and thanks for the answer and putting us out of our misery !!