Have you noticed that the relationship panel seems to be inconsistent in showing all of the Sims known to your Sim? At any given time, I have had Sims show in the phone who are not in the relationship panel, and vice versa. Later, the Sim who was missing from one place or the other will show up again. I've also seen the Chat and Invite to Current Lot options missing from various Sims at random times, only to show up again later. Is this a bug or by design, and if deliberate, what determines when certain Sims or interactions are available or not?