Belle never imagined that Rumpelstiltskin had been mourning her - and mourn he had. The girl who'd walked into his shop earlier today hadn't known what to make of Mr. Gold's effusive reaction (except to intuit that he meant to protect her, whatever his reasons), but Belle has lived with the man for almost two years. No matter what face he wears now, she can read his emotions as she replays the memory.
He's truly believed she was dead, all these years.
She might have been jailed away, but Belle has the feeling that he's the one who suffered the most.