To access the Recycle Bin, the instructor would log into the course and click the gear icon in the upper right-hand corner of the course. Then, the instructor would select "Recycle Bin".
We believe we see the Assignment in the list of deleted content.
When the instructor identifies the Assignment they need to recover, they simply need to click the up arrow icon (circled in the screen shot below). That button will allow the Assignment to be recovered into the course.
One thing to note is that items will only be in the Recycle Bin for 7 days. It appears the instructor deleted the Assignment on Sunday, November 29th. As long as the instructor recovers the Assignment by Saturday, they should be all set.