I'm really sorry that your cat Jasper is missing too. I know how it must feel. At home in Germany my father died. He was the closest to my cat. The day he died my cat Blacky took off. He didn't return for 5 weeks. My Mom looked everywhere for him. It was in such a hard time (having lost her husband that she had loved for 37 years) and now Blacky was gone. She looked everywhere, at the shelter, the neighbors..., she posted signes. Than after 5 weeks he was found skinny likes bones in the bushes of a neighbors' yard. Mom took him to he vet and he got a shot to give him some energie. She fed him well and gave him lots of love and he got all better again.
Lots of love and luck to your little one!!
Gabi