In Harry Potter the Deathly hallows Part 1.......?

I was wondering when Harry, Ron and Harmione get captured by the snatchers, they take harmiones book, and the snitch from harry BUT in the basement Ron still manages to pull out his diluminator. Why didnt they take that? Is it mentioned in the book? (i an only on the 4th book) I was just wondering. Yes it seems a bit tedious, but i was just wondering is all.