Google Places has a huge effect on search results, which we've addressed before with the significance of optimized place pages and user reviews. Well, it was only a matter of time before the blackhat SEOs manipulated the system to their clients benefit. Fake negative reviews have been a problem for many companies, and now the new tactic is to go to competitor listing pages and mark the business location as "place is permanently closed."
So far, the only troubleshooting you can do for this is to periodically check your listing, and to report to us if any suspicious activity occurs. We will also be checking your listings, but an extra set of eyes won't hurt! Hopefully Google will enhance Places communication in the near future and notify business owners of any settings that are modified on their listings--especially to verify that their place of business is in fact closed permanently.
Remember, your team here at Tandem is here to help with any questions or problems you are having. Do not hesitate to reach out!