Obviously do not know why you have been asked to do this but can reassure you that this has happened to more than one of my colleagues and they have been ok. It may be that the film was taken at a slightly wrong angle and a small part of the lung has been obscured. If they have a doubt as to the validity or integrity of the film, they will always ask for the xray to be repeated, not just by a radiographer where you are but also don't be surprised if they then ask you to do another on arrival just to confirm that all is well. Good luck and don't be put off QP-they have been fantastic employers to us, they just have their own way of doing things.