I didnt notice at the time, it has been cleaned again twice since that first time. The last time I cleaned all the dust off just using the rocket blower except for 2 stubborn spots which came off with a quick brush with the sensorpen.Did you swipe it diagonally. I can see the swap streaks.
I love my Sensor gel stick. Much easier and no chance of leaving any smeary residue. It's reusable and after several uses very cost effective compared to the swab-wipe technique.
How to Use the Sensor Gel Stick
I have been contemplating buying one of these, was just waiting to hear a few more user reports. If you are still using yours and are happy with it, I might just go ahead and order one.
I cant find anyone stocking it in Australia, but on ebay asia there are a few for sale.