Early seed production

ive got a female staiva in flowering with my autoflowering male indica right now.

a fan blows pollen (purposely) all over the girl to give me as many seeds as i can get. however, the sativa responds slowly to the flowering ques, and is only just beginning to show sex after 1.5 weeks of hps.

this is all well and good except that i found a seed today. a single seed sitting in the nook of a tuft of leaves...

im assumeing its her own seed, but how the helld it get there when no other seed pods appear even half-grown?

PS: it was an overly small, beige seed that looks crappy, but still....