Leaf growing out of leaves

Yep, quite "normal", cannabis can do all sorts of strange things like this, as well as growing buds on leaves, growing buds on leaf stems, multiple leaves from a single point, self topping of branches, three node branches on only a single branch of the entire plant, etc, etc. If you are keen, I have posted a few pictures of abnormalities in my diary "cannabis conundrums", in week 7. They are quite fascinating and may give you an idea as to what "normal" is for cannabis. All these freaky mutations are not a problem, the plant will grow and flower as usual, with no loss of yield or potency, just a bit of "individual expression" going on. I would have loved to have seen your leaf out of a leaf in pictures. Hope this helps, Organoman.