The joy of street parking

I had to leave the house early today in order to move the car which was parking on a "Wednesday spot". After roaming around the block where the car was suppose to be, I finally realized that the car was stolen or got towed. Looking around more carefully, I have noticed a SFDC small sign, stating that on October 30, no cars are allowed to park 3o feet away.
I could swear that when I parked the car on Sunday, the sign was not there, which means the sign was put on either Sunday or Monday, leaving me 1-2 days of notice...
According to the code violation, the sign was put due to an event. No clue about what kind of event was provided.
Long story short, I had to go get the car from the towing garage on 7th st. and leave these people $320 Halloween present.
I guess it's bad luck but I have never thought that such thing could happen.