Some, but not all, plants can be propagated from just a leaf or a section of a leaf. Leaf cuttings of most plants will not generate a new plant, they usually produce only a few roots or just decay. Because leaf cuttings do not include an axillary bud, they can be used only for plants that are capable of forming adventitious buds. Leaf cuttings are used almost exclusively for propagating some indoor plants. There are several types of leaf cuttings. Leaf Cuttings, Leaf-petiole, Leaf without a petiole, Split-vein, Leaf-bud Cuttings, and Cane Cuttings.
Allright that being said. if your cutting doesnt contain axillary bud (or in other terms a cutting with a node or multiple nodes) the plant species must be capable of forming adventitious buds and sadly hemp/weed does not! Now lets explain this further. The genetics of a plant is in simple terms is a recipe the plant follows as it grows. Now in a plant that can form adventitious buds it can do this because all the cells of the plant have access to the recipes for roots,leafs,steams and everything else. Where as the majority of other plants parts know what and how there supposed to grow without "knowing" the recipe for the entire plant.
If this worked for weed even just a little bit then these and every other weed forum would be loaded with photos from all over the world showing single leaves growing into plants and no one would be baking or making hash with leaf either. I am even begining to feel its been a waste of time to explain what I have anyways. Cause even if by some miricle of nature this worked you have gained nothing. It will take more time and energy to root out and grow than a normal clipping would because steams and roots take much energy for the plant to produce and a properly taken clipping has a much much bigger head start on steam structure.
Where is this guy growing anyways if he even is? I mean I have a very small space now but even back when I had the whole 2nd floor I still found myself spending loads of time cutting and triming to best suit the space and I have thrown away more clippings than I could possibly ever root without stressing the mothers if much at all.