Canon indicates thata vanished items do reappear. In Order of the Phoenix, Fred and George force the Slytherin Quidditch captain, Montague, into the Vanishing Cabinet (the cabinet that Draco uses in Half-Blood Prince to get the Death Eaters into Hogwarts).
‘Malfoy just docked us all about fifty points,’ said Harry furiously, as they watched several more stones fly upwards from the Gryffindor hour-glass.
‘Yeah, Montague tried to do us during break,’ said George.
‘What do you mean, “tried”?’ said Ron quickly.
‘He never managed to get all the words out,’ said Fred, ‘due to the fact that we forced him head-first into that Vanishing Cabinet on the first floor.’
Hermione looked very shocked.
‘But you’ll get into terrible trouble!’
‘Not until Montague reappears, and that could take weeks, I dunno where we sent him,’ said Fred coolly. ‘Anyway ... we’ve decided we don’t care about getting into trouble any more.’
Order of the Phoenix - Chapter twenty-eight, Snape's Worst Memory - Page 552 - Bloomsbury
While Harry is receiving Occlumency lessons from Snape, Draco enters the room to tell Snape, rather excitedly, that Montague has reappeared from being vanished, and is jammed down a toilet in one of the boys' restrooms.
‘They’ve found Montague, sir, he’s turned up jammed inside a toilet on the fourth floor.’
‘How did he get in there?’ demanded Snape.
‘I don’t know, sir, he’s a bit confused.’
‘Very well, very well. Potter,’ said Snape, ‘we shall resume this lesson tomorrow evening.’
Order of the Phoenix - Chapter twenty-eight, Snape's Worst Memory - page 563 - Bloomsbury