Facebook.The supermarket giant has launched an investigation after Ana Palmer said she was confronted by a staff member after she posted on social media about having her bags searched at the branch.Plymouth Live reports that Ana was searched in Tavistock, Devon in December and was told it was due to an increase in 'mystery shoppers' - someone who visits a shop or restaurant in order to assess the quality of the goods and services.She took to a local Facebook group to post about her shock over