If your invitee is not in your Garden, there are 2 explanations.
All the Seed positions have been taken and your Garden is about to cycle. There is no more room in the Garden. Your invitee is in a Garden of your descending line.
You have been Harvested and are now in the Perpetual Garden. Your guest is in a Garden of your descending lineage. This is called pollination.
Pollination allows you to help your community automatically.
In fact, the algorithm will find the Garden that needs help to finish filling the last few Seed positions and cycle the Garden.
This way, all the Gardens in your community are in perpetual motion.