Answer Question
There is a third party trick to disabling this optionhttp://time.com/3692029/facebook-tricks-tips/Maybe they did that
What does the "Last Active" time stand for on Facebook Messenger mobile app?
Can the last active time on facebook be wrong?
Facebook messages/friend last active?
Who can see my last active status in facebook messenger?
How do i hide "Last Active" time stamp facebook messenger mobile app?
Is there a way of turning off the "last active" in facebook messenger?