Prius (2004-09) :: Thin Coat Of Oil At Bottom Of Filter / No Leak Found

Maybe I am running out of my beginner's luck. Recently when I did the second oil change at 10K miles, I placed the drain pan without taking into account the fact that the oil drains partially sideways. The oil stream ended up splashing off the edge of the drain pan and made a mess. Then I did not withdraw my hand fast enough when unscrewing the oil filter and allowed a stream of oil running down my arm and staining my new shirt. The I filled the new oil filter too full and had one more spill when installing it.

About two weeks later I found there was a very thin coat of oil at the bottom of the oil filter but no drips either on the filter or on the ground. I checked the oil level and it was the same as before. I checked the filter tightness with a torque wrench and it was also as tight as before. I wiped the bottom of the filter clean with paper towel. Now about another two weeks passed and a corner of the bottom of the filter is coated with oil again.

I am thinking maybe it was just the spilled oil gradually making its way from the (outside) top of the filter to the bottom? If there is a leak then I should get at least some drips, not just a thin film every two weeks, right? I also thought about untightening the filter and then tighten it again but I was afraid of large amount of oil coming out, would it? Also I had carefully checked the o-ring and wiped the flange clean before installing the filter and there are so many threads to screw the filter on - it is hard to imaging the filter would not seat correctly.