If you experience a crash or other issue that causes you to lose your Beyond CAD scene, unfortunately there may not be much you can do. Feel free to contact support but even then we may not be able to help you.
The best solution for avoiding lost data is saving your Beyond CAD scene often and occasionally saving as a different file name so you can revert to a previous version of the scene if necessary. For example, if you save your file as Lake View Roundabout, save it in the future as Lake View Roundabout 2 and later Lake View Roundabout 3. This may take up more disk space with saved files but will give more options to return to previous saved files in the future if you lose data.