Because bob's remains were eaten by hungry spiders, a similar fate which tragically befell all of his family 2 years previously. As they were recluses who shunned contact with the outside world, no-one knew of their existence. With no documentation or ID in their self sufficient community, in the eyes of the world, bob's family simply didn't exist
Bob then tries getting out of the friendzone by buying his crush a dozen roses. When he gives them to her she says "How sweet youre like a brother to me! Thank you!" ?