My first season in the League, I had a match (against MtMagus I believe) that ended 3.5 - 2.5). Here's the game that ended in a tie:
http://gokosalvager.com/static/logprettifier.html?http://dominion-game-logs.s3.amazonaws.com/game_logs/20160226/log.0.1456455696564.txtLong story short, if you look at my last buy before the game ended, I bought a Silver instead of an estate. I was at the end of my shuffle, and I thought "hey, Estates aren't going to matter, it's going to come down to who can spike that extra province, so I want a silver". I overlooked that I just emptied the third pile, and an estate would have given me the win. So we tied.
This is not a misclick, it's not even quite the same as the example you provided, this is more my fault and not the fault of some strange quirk that happens in MF. But my point is that in an IRL game, it's much more apparent that there's 3 empty piles, and I probably make the right decision. Probably my opponent also will just acknowledge that I win.
In a league game though, it's a tie, there's nothing I can do. My opponent said "what happened? You could've bought an estate and won?" I told him what happened, and part of me wanted him to say "you know what, we'll give you the win, because you should've won that game", but he didn't, and shouldn't have, and even if he had, I would've told him no, it's a tie, it's my mistake. I had another league game recently, I can't remember the situation exactly, but my opponent lost because he misclicked a Tournament and was forced to gain a Duchy, which emptied the third pile, and he lost. He would have otherwise won the game. We discussed it afterwards, ya that sucks, but I wasn't giving him the win (and he didn't ask for it). That's just the way things go. Sometimes you don't get the wins you deserve, or you get wins you don't deserve. All you can do is try and learn from your mistakes.