I'm guessing it's a security thing. Maybe he was crate trainged before and he's hanging on to it for his secure place? If he wasn't crate trained prior maybe being a rescue he's just hanging on to that as his steady item? The humping might be a dominance thing to say to the bed I'm the boss, sort of an insecurity over his changes. I wouldn't worry about it much unless you've had him for awhile and he's still doing it.

My best bet is it's just nerves. That's the one thing he had prior to coming to you and he feels more secure with it.

I can't speak from experience but I'd guess it is a security thing like eicnan said. Eventually I imagine he'll give it up, but in the meantime, I'd indulge it as long as he needs it until he starts feeling more comfortable. ADORABLE little guy, btw!

I rescued Casey Jones over 6 years ago and he's always sucked on something. He was about 2 when I rescued him. I thought he may out grow it, but he never has. In fact, he's currently laying in the middle of the living room floor and sucking on his red blanket.

OMG!
I adopted Fidget in April- she is estimated about 3 years old.
She stole one of our kids' stuffed animals- a large cheetah- and carried it around like you describe with sammy-
she does this 'nursing' thing- she looks like a kitten- suck-suck-suck and knead with her front paws.
she would occasionally hump it too- and it was always with her.
our pit bull- who loves all toys- wouldn't touch it! i think she was grossed out! lol!

Fidget has since gutted it, and has been sucking on other stuffed toys here and there.
we thought she was just broken- but maybe it's a boston behavior? she's our first...

(and congrats!! he's CUTE!)

Awww....poor baby :( Where did you get him?