I searched google for "police acknowledgement mistake" and several variations. The closest I could find was people calling for the police to acknowledge their mistakes. I can't find the police doing it themselves.
edit: https://www.google.com/search?q=%22police%20admit%20to%22
170,000 results
Though it doesn't give a number of results explicitly there are still several pages of results (though they'd need to be deduped)