I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
Twenty-four hours notice is required for metered spaces, but if you were in an unmetered space, they actually have to post the signs 72 hours in advance (which makes sense, because people tend to park for longer when there's no meter). You can fight the ticket on the grounds that there was no notice provided 24 hours before the car was towed. That involves testifying as to the last time you walked by the car and the fact that no signs were posted. If you know anyone else in the area who passed by and can testify that the signs weren't there, that may also help. Look at the time on the tow, because you'll need to have passed by the area within 24 hours of when they took it for that to be a defense.
To prove that notice WAS given, they'll have to bring in the person who posted the sign to say what time he did it.
Since the ticket is illegal, and the tow is illegal, you also have the ability to sue the city for the towing and storage fees. You may want to call the City's Attorney's Office to see if they will reimburse you without making you file a lawsuit first. If you get the ticket dismissed before calling them, that may help.
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