Its going to take awhile for the oil to come back into view after the engine has been run. When the engine is running, oil is caught by the gears in the primary drive and tranny and slung about. Unlike on an air compressor pump, it can be a couple hours before it all drains back into view in the sight glass.
What I do on my Blasty is check the level before I start the engine in the morning, be sure its full, go ride, and check it again the next morning. As long as your crankcase is airtight, countershaft seal is still good, and you don't have any other tranny oil leaks, you won't lose any oil even if you don't see it in the sight glass right away.