Cream duvet cover with navy piping, Queen size

I lost my cream Marks & Spencer 100% cotton duvet cover set, Queen size, with navy piping and a tiny monogram 'LP' stitched in the top left corner. I last had it yesterday around 3pm after I popped out to Briggate near the Corn Exchange in Leeds to grab a coffee; when I got back, it was gone from my bed. The cover is in good condition overall, just a faint coffee stain on the inner seam and a tiny snag near the zipper. This duvet set was a gift from my mum and it really matters to me to get it back.