Gray tabby cat with white chest, lost near Cascades Park

I lost my gray tabby cat with a white chest yesterday around 3pm near Cascades Park in Tallahassee. He's medium-sized, short fur, with a small notch in his left ear and a light-blue collar with a tiny bell. He slipped out of my porch on West Pensacola Street while I was unloading groceries and wandered toward the Capitol area by the bus loops. I'm really worried—this cat has sentimental value; he was a gift from my grandmother and means the world to me. If anyone spots him around the Capitol area or near campus, please let me know.