How to Un-Trash Tasks
If you trashed a task by mistake, you have 30 days to retrieve it from the bin.
With the list in question active, click the List Options Menu, then select "Un-Trash Tasks".
You'll be presented with a list of all of your trashed tasks for the current list. Press the "refresh" icon to un-trash your list.
Your task will be placed back in your list in the order you left it.
Trashed tasks are stored for 30 days or until you manually delete them from the Trashed Tasks list.