Lily, I looked closely at your single leaf and thought it looked like the leaf had been broken off away from the juncture of leaf and stem. I usually remove leaves right at the juncture where the surface area for callusing is smallest. I don't usually have luck with rooting from a callused area somewhere along the leaf body.
You might try just hanging onto a leaf toward the bottom and twisting slightly to separate leaf from the stem at the juncture. Then let callus for at least 24 hrs. Then lay leaf on top of dampened soil and let sit till it roots. Only then do I make a shallow hole and insert rooted section of leaf. The rest of leaf does not have to be buried. Also, if you can stand it, try and twist a few leaves off to callus. That way there's more of a chance that at least one leaf with root. I think the transparent look to the leaf does not bode well but can't be certain so just keep monitoring that leaf while you get other ones going if you have the mind to. Good luck.
