If you decide to exile a token, it will cease to exist the next time a player gets priority. Then, when Witch's ability tries to return it at the end of the turn, it is no longer there. Even if it was, a token cannot change zones gain once it leaves the battlefield so once it is exiled, it can't leave Exile.
Tokens can only exist on the battlefield. If a token is sent to any other zone it ceases to exist right after it reaches that zone.
110.5f A token that’s phased out, or that’s in a zone other than the battlefield, ceases to exist. This is a state-based action; see rule 704. (Note that if a token changes zones, applicable triggered abilities will trigger before the token ceases to exist.)
110.5g A token that has left the battlefield can’t move to another zone or come back onto the battlefield. If such a token would change zones, it remains in its current zone instead. It ceases to exist the next time state-based actions are checked; see rule 704
Mistmeadow Witch
If you decide to exile a token, it will cease to exist the next time a player gets priority. Then, when Witch's ability tries to return it at the end of the turn, it is no longer there. Even if it was, a token cannot change zones gain once it leaves the battlefield so once it is exiled, it can't leave Exile.
110.5f A token that’s phased out, or that’s in a zone other than the battlefield, ceases to exist. This is a state-based action; see rule 704. (Note that if a token changes zones, applicable triggered abilities will trigger before the token ceases to exist.)
110.5g A token that has left the battlefield can’t move to another zone or come back onto the battlefield. If such a token would change zones, it remains in its current zone instead. It ceases to exist the next time state-based actions are checked; see rule 704