A message to me / my homework assignment got lost
If you feel like a message to you or assigned homework have been lost, you have probably marked it as "done" (perhaps by mistake). These types of messages / homeworks do not appear in the list.
In order for all messages/homeworks to appear in the list, click the 3 dots in the upper right corner and tick the "Show done" feature. "Done" messages are marked with a green pipe.
You can mark the message as done either by sliding it sideways, or by clicking on the message and pressing the "Done" flag.