I had one of those moments a few days ago.
I was with Heimerdinger pushing top lane and my adc was mirroring me on the bot lane. I clearly counted 4 opponents in front of our 3 teamates in mid lane. We were all about at the outer towers (all took down already).
Vayne got attacked and actualy had a kill. I figured that obviously if both of us keep pushing, 1 of the 2 towers would fall and the death would worth. So I kept pushing and vayne did the same on her side.
Well... I got attacked and killed by 3 champions and vayne got killed by their mid laner on bot lane.
The 3 bozos in mid ? Well... they fled back. From the terrifying 0 opponents left mid. They didnt warded, they didnt kept vision of anyone, they didn't farmed any camps... nada... they just backed and "Wait for regroup". Needless to say I lost that one lol...