Hi there
@THCandME What I believe happened was your plant produced a male pollen sack and pollinated the bud it popped out of resulting in the seeds you found.
It's possible the pollen spread Check the remaining buds for swollen calyxes and see if any seeds are growing in them Otherwise wait and see at harvest. It's not that an uncommon thing to get a few seeds every now and again
when using feminised seeds Hope is answers your Question and Happy growing