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