This really happened, not long ago...I'd just left after an appointment at the Jobcentre (fellow Brits will know what I'm talking about), and I was halfway up the road when I realised my backpack wasn't on my shoulder, so I went back down to the Jobcentre to see if it was there. When I got there I found that all the Jobcentre staff were stood outside the building for some reason. When I asked one of them why, she told me that the building had been evacuated because someone had found an unattended bag under one of the desks, and they had to evacuate in case said bag had explosives or something. The bag was my backpack...I nearly died of embarassment.
For a moment I even thought they'd get the police involved, but thankfully it all got cleared up. One of the staff even said I'd done them a favour by making their day a bit more exciting, lol.