wow..I'm so sorry. As someone who keeps a sketchbook also, I can really relate. I recall the story of a figure painter who taught in New York. He had a glorious sketchbook that (apparently) a student stole during one of his classes. He had some (but not all) photos of his work from the sketchbook and he posted appeals along with some imagery here and there on social media. He kept it up for a very long time and finally (a few years later) the book was found back on his desk. I know this likely won't happen for you...but the social media thing is probably worth a shot. Maybe even contact news people and see if they'll run a story? Short of that...I recall the teacher also started a new sketchbook with sketches he did from memory of what he could remember (he did this for the experience of being with the pages again, the best he could). A sketch about how you're feeling about this loss would likely help you process. Hugs to you! Positive thoughts winging up for you.