path converted in image

Hello Community,

don´t know how I managed to "delete" my path. But i opened a file and some of the Illustrations I made are now an pixel-based image, no vector anymore. All of the paths and the work is gone. I could retrayce the images but the quality won´t be the same. I have the feeling there won´t be a way back, but I still would like to know what happend, if there is such a function like vector to image, so I can be aware of it and avoid it. or is it a Bug

Thanks for any help and your comments!