There is no special name.
You call them up or do something to let them know how special they are and how much you miss them.
A very special person is someone who you deem as special to you. Some people will call their friend a special friend, or say that their lover is special to them. There are many reasons why someone would be consider special to another person.
There is no special name for someone who studies Hebrew.
There is no special name for a person who likes squirrels.
You would call someone who looks after sheep a shepherd.
A deformed platypus
genious
a kangaroo
you would call someone chuckles when he or she laughs and there tummy bounces up and down
You would call them someone who peruses.
I would call him a hobbyist.