I'm not sure if I can show you a way to get the actual deleted content via API, but I have some other methods that will get you other details
First, does your community have the Records Retention service? You would have to be licensed for this and collecting that data in another system. This would capture all actions, from creation of the comment, to an update, to the deletion. You could tie together these actions to see the original comment
Next, in the admin console, you can go to System -> Management -> Audit Log Viewer, and this will give the history of different actions. This may be a difficult search because there is a lot of activity, but it may identify who and when deleted the content.
Lastly, you go use Jive's Data Export Service, which will allow you to query all activity and filter by action, so you can filter on the DELETE action on a comment. More information Using the V2 Jive Data Export Service (Analytics) and How To: Use the Data Export Service API Explorer