A secret passage could lead to the Room of Requirement for anyone who is in need, and I guess we need help.
Argus Filch knows at least about 3 secret passages where the destination is unknown and due to the lore there are at least 7 passage ways out of Hogswart. So there is a lot of opportunities for J.K. Rowling to fill in some blanks and expand the universe.
Potterhead here. Let me highlight this.
The known, traversable passages to exit/enter the castle would be:
1. The one-eyed witch statue, which goes into Honeydukes
2. The tunnel under the Whomping Willow, which goes into the Shrieking Shack.
3. The portrait of Ariana hanging in Hog's Head, which connects to the Room of Requirement.
4. The vanishing cabinets (loosely), connecting the Room of Requirement to Borgin and Burkes.
5. An undisclosed passage by the statue of Gregory the Smarmy from Hogwarts to who knows where.
If I were a betting woman, I would say the Whomping Willow would fit best with the scene. HOWEVER, that is assuming we are trying to get into/out of the castle. The Hogwarts grounds are sprawling and full of secrets in the books - they could do just about anything and get away with it.