It is possible that I did as you say. It has been a tiring day. Hiked more than 5 km with my pack (20 kilos) and the exhaustion extended itself all the way to my brain. I will never know for sure. I can only try once more with a bit more care.
At least I am comforted by the fact that because it is not black I can be confident that my equipment (holders, bellows, changing tent, tubes) is defective in some way that light leaks in.