- Player A plays Roar of the Wurm
- Player B plays Astral Slide
- Player B recycles a card and returns the Wurm token
What happens then?
Tokens disappear whenever they leave the battlefield. The relevant rules are:
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.
So the Wurm token would be gone for good in this example.