pollen sacks don't just pop out and release. Females usually show first.

For females, you'll see one or two white hairs, like you'd see in a bud at the junction of the stem and a branch near the top of the plant. If growing from seed, I believe it takes at least a month after sprouting to show. They have to hit a certain chronological age, 12/12 or not.

there is a good example here with a pic of male preflowers
What are preflowers? - 420 Magazine
copobo Reviewed by copobo on . Timing of staminate flowering. I've got some indica plants (4) grown from seed that I put into flower 5 days ago, and had some questions about determining sex. I don't know what strain they are, or even if they are all the same strain. The seeds were unidentified freebies I got with an order. I can tell they are indica or indica-dom by the leaves, but not much else. Two of them grew abt twice as tall as the other 2, but I don't know if they are a different strain, or if they are taller because they are male. The leaves are Rating: 5