Tenth man

At shacharis in the Vercingétorix synagogue in Paris on Friday, I could only see nine people, including myself, when the chazzan reached the end of Pesukei deZimra, so was very surprised when the chazzan then lanched into ḥaṣi qaddish then בְּרָכוּ, as these cannot be said without a minyan. But when I looked closely around the room, and concentrated very hard, I found myself seeing the faint ghostly outline of a tenth tallith-wearing man.

No, I wasn't having a mystical experience. The faint ghostly outline appeared in the glass doors of the bookcase at the front, and the man whose reflection I was seeing was hidden from me by a pillar.