Posted on behalf of my colleague, Lora Pabst:

Over the past year, hundreds of you have asked Whistleblower for help. While we can't investigate each tip, we want to share more of what you tell us. In 2009, we started publishing a few tips each week to stimulate online discussion and create ways for our readers to help each other. Unlike our news stories, we have not verified this information, so we do not include the names of the parties involved. If you have a tip, send it to whistleblower@startribune.com.

Whistleblower hears about a lot of parking and towing problems, but complaints about some downtown Minneapolis parking lots have us wondering whether there's a bigger problem with lots that require drivers to leave their payment in an envelope.

A woman who parked at a surface lot said she paid for her parking by leaving money in an envelope and depositing it into a drop box. When she came back, her car had been towed and the company that manages the lot told her they didn't have her money.

She had to pay $231 to get her car back because she couldn't prove she paid. It was her word against theirs.

Has this ever happened to you? How can you protect yourself? Post a comment here or send us an email.