Hi @anon58291950, welcome to the Asana Community Forum and apologies for the inconvenience here! Moving a task to the later section in your My Tasks shouldn’t remove its due date. When you open the task, could you scroll down to the tasks changes and see what was the due date of the task?
If you still cannot see the previous due date of the task, I recommend you to contact our support team and share the URL of the task in which the due date was removed. When you contact them, you can share the URL of this thread to speed up the process!