When a rumour is removed, the rules say it is returned to the "token pool" (LtP p.16). As I can't find a definition for Token Pool I guess the token is not returned to Dracula, meaning they are a one use item once gained?
It makes no difference. There are 4 rumour tokens provided in the game. Dracula receives 1 at the start of the game and a further token whenever a despair token is placed (this will happen a maximum of 3 times).
There are no other ways for a rumour token to be gained, meaning that there are enough tokens in the mix for all eventualities, so once discarded, rumour tokens are essentially out of the game, wherever they are returned to.