The question isn't whether or not the propagule will form roots ..... it has a large adventitious root already attached.

If the propagule includes a node (it appears it does), it is capable of producing a complete plant. If it doesn't include a node, it can only produce a plant if the species is capable of de novo regeneration. Though it doesn't look like it's simply a leaf cutting, I can't see what's in the bottle.

Something I wrote about the topic:

Cuttings (leaf)

Many plants can be propagated from leaf cuttings. The pivotal point is whether or not the propagule is capable of forming adventitious buds. Some plants have groups of cells that descend directly from embryonic cells engaged in meristematic activity. These cell groups can differentiate into buds/shoots from foliar embryos that formed as the leaf was forming. More commonly though, wound-induced secondary meristems can form when existing tissues already acting as part of an organ dedifferentiate into NEW meristematic regions (de novo regeneration), then redifferentiate into new organs (buds).

If you want to be fairly certain that you'll be successful in your cloning attempts, make sure you include a latent or actively growing axillary bud, which would be located just distal to (above) where the leaf is attached to the stem. The downside to propagating from stem cuttings with a singular leaf in water is that often the bud is destroyed by rot, and/or, the type of root tissue that forms in water is physiologically very different from root tissue that forms in a solid, well-aerated medium. This difference is made manifest in the water-formed roots being very poor at taking up water from a solid medium, along with the fact that water roots are very delicate, almost brittle. As such, they handle the transition from water to soil poorly.

Many leaf cuttings will readily produce roots to form 'blind cuttings', which means they are incapable of forming the adventitious buds which are prerequisite to shoot formation. I don't know if your plant is one such, but if it lives on and on w/o forming a stem, you'll at least know the reason.

To reiterate, it's best to bring an existing bud along for the ride or be ready for a disappointment. Blind cuttings can live for years, but eventually they collapse for no conspicuous reason.

Al

Your rescue looks amazing! Well done!

No harm trying to propagate the unintentional cutting. You've got a gorgeous mama plant that will be able to give you many more propagations should you need or want them later.

If it were my plant, I would sprinkle a little bit of cinnamon on that open wound.