Lost a reply while typing

I was typing a reply to a post, almost finished it, when the window scrolled, and the message I was typing was gone, then I noticed someone else had replied to the same post, possibly at the same time as myself, his post appeared 3 times for some reason. 
my post wasn’t to important, but I wonder if it had been a long post from someone, it would have been upsetting to lose it. Is this just a one off ? Or could it be a problem if two people are replying to the same post at the same time ?