I accidentally deleted a Class Chatter Message with 26 responses regarding the death of a classmate. Is there a way to reload a backup of the website or recover this message? Thank you.

Unfortunately, no. When you click the delete button, a warning that pops up and states: Are you sure you want to delete this item? This is so that you have an opportunity to decide if you really intend to delete the post. In this instance, unfortunately the data is gone.