Yeah, especially with such a strong vortex, you won't see much in the way of krausen. I would suggest that in the future, you run your stir bar as slowly as possible. I only spin fast enough to show a small dimple in the surface. With some yeasts at that speed you will see krausen form, especially WLP001. I have lately moved to the Shaken Not Stirred method.
One indicator, if you don't want to check gravity, is to check pH. The yeast will drop the pH of the wort fairly quickly, indicating fermentation.