I'm going to guess from your post that you have a species phalaneopsis, perhaps an equestris. I can only tell you what I would do if it is, indeed, a Phal. equestris. I'd plant the keiki in sphag moss so as to control the moisture. Keep it damp at all times.......not wet, and don't let it go completely dry. New roots should start to show up soon.
Hope this helps,
Al
I would agree, though you may want to wait until the keiki has at least another root so it can survive on its own. Another option is to 'stake' it down in a smaller sphagnum-filled pot, while it is still attached to the mother plant, and only separate it from the mother plant once it has established itself.