I just won against a Riven playing as a Vi

The only way Riven loses to anyone is if it is a bad Riven.

Statistically you should have won so it should not be surprising.

I don't see how you can't beat a Riven specially if you're tanky. More health, tanky ( specially with thornmail ), and if she has armour you can easily break through it with your W, you can also zone her out and cc her with your Q and R ( she got no where to go! ). Easy peasy lemon squeezy.

It was a bad riven. Tell me their ign so I can smack them irl... Jk https://youtu.be/gcKHiAs_QZI

The reality of the situation is "I just won against a Player while playing as a League of Legends champion". So it was supposed to happen. Or not. It's one of those...

were you playing top or jungle? jungle vi makes riven useless in teamfights so you should win

As a vi top enthusiast i will say something- Vi's early damage is insane. 2 of her abilities cause armor shred making riven even less tanky than she was before. You can easily hit her from range with your E and your Q + autos will cause your W to prock which leads to massive damage. Also as vi you have a ton of CC which as a riven player is one of the worst things a riven can face. Tons of cc+ Your damage means an easy win in lane