Another reason to believe it really heppend is that China had not had a pure military satellite for many years. The recoverable satellites were for reconnaissance purpose in 70s and early 80s, but their role was changed to civilian imaging and microgravity experiments more and more from late 80s. Analysts in the west suspect China has been developing new military imaging satellites and early warning satellites. I'm also sure there must be some military space projects undergoing. In the online forum on Internet, people have talked about this launch but no one can provide the evidence that it happened.
Someone believe it was an early warning satellite.
Suppose that launch really took place. The payload could be an early warning satellite. Unfortanately, there is still no evidence that could comfirm it. I tried to collect clues from Internet and other sources. But the result brings me to an opposite direction.