How to track and reopen unanswered conversations

I have recently test the implementation of Social Media in Zendesk and one of the main issue I am facing is that some agents are updating tickets (by clicking on Submit) and forget to click on Send to answer the Social Media conversation.

It's indeed quite easy to forget to click on Send and think that clicking on Submit will also send the answer as this is the way it works on Emails.

I have been looking for a way to track those unanswered conversations but I am not able to do it through triggers or automations.

It seems I am missing conditions based on answers Sent through the messaging system.

Could you please help ? 

Note : I have also open a support ticket (without solution proposed for now).