Why does a conversation seem to disappear from my Inbox?

If a conversation seems to disappear after you open it, check the later pages of your Inbox. Opening an unread conversation marks it as read, which can move it to a later page when you have many unread conversations.

Why this happens

Unread conversations are grouped before read conversations. Within each group, conversations appear newest first.

That is why an older unread conversation can sit above a newer read one. The conversation you opened has not disappeared. It has moved farther down that order.

How can I spot conversations I haven't replied to?

Professional Cuddlers see the subtle gray reply-arrow at the far right of an Inbox conversation row. It appears when the latest message in that conversation came from the other member.