Silver Yamaha trumpet with green engraving and initials AM

I lost my silver Yamaha trumpet yesterday around 3pm outside the Ashmolean Museum on Beaumont Street in Oxford. It's a Yamaha YTR-2330 with a silver finish, a small dent near the bell, and a bit of tarnish on the valve casing. The bell has my initials AM engraved, and there's a tiny scratch near the third valve slide; the hard case is black with red lining, and inside is a spare mouthpiece with a light blue cap. This trumpet is sentimental to me—it was a gift from my late aunt—and I really need it back.