Its not drophack.
Its some kind of bug that happens. I've had it several times and it seems to be when a player from opponents team leaves the game - sometimes the freeze is just a few seconds and sometimes it can be 1-2 mins. I'm not sure why this is happening, but its not hacks.
Although I do understand its confusing to get a "defeated" sign, as you say, in the end the system figures out what is going on and gives you the win.
Yea I know it happens naturally but this was weird as the guy on the other team was whispering "ping ping ping" at me is all.