About a boy (teenager) who put together an egg-shaped spaceship. A face-less person welcomed him into this “lost (and found)” world where it rained at night and you could do anything except skydive which really bugged the protagonist. They told him this place was limitless (or something) but he found the ‘edge’ (there was a crack in it?).
The deal was they had to sort all this lost stuff from the real world, like they’d choose whether the owner would forget it or they would send it back so the owner could find it.
He met a girl who always wore a helmet (which was because she was in a coma after a biking accident).
In the end he finds out you not only get send lost things but you can send lost people back (but with the drawback that someone else has to die), so he makes a deal with his friend (who remembers she’s in a coma) that she’ll send him back and die, last minute he gets given his dads sun glasses that he’d lost, and crosses back into real world.
The book ended like there was going to be another book after it because I remember feeling like it was suggesting that the girl survived.
I read this in 2011, it’s a children’s/teenagers book, not sure of the author or the title. The cover had the egg space ship on it, I think, navy and a bit of red maybe. I also feel like the name David might be in it somewhere.