We've had exactly the same happen here. First my husband cleared all the nearby pavements to help both the neighbours and myself (I'm heavily pregnant and don't want to slip!) and the person parked outside our house cleared the snow off his car all over it so it was icy and dangerous again.
Then once that car left, our neighbour kindly repaid the favour by clearing the icy/snowy parking spot for my husband (and the extra snow off the pavement!) so he could park outside our house and it would be easy and safe for me to get to the car and back.
Of course, selfish lady over the road took the spot before he got home because she preferred the look of our spot to her own icy, uncleared one. So I now have to navigate the dangerous uncleared parts of the road and paths to get to the car. Which will be great if I need to rush to hospital in the middle of the night! (we're having a lot of complications).
I understand it's a public highway and don't usually get too bothered by parking, but nicking someone's cleared spot is just plain rude. They could have cleared it to help a pregnant wife, elderly neighbour etc. Dig out your own spot and stop being so lazy and mean!