Here's why:
* The Mansion is Designed for Linear Progression: The game's design intends for you to use the Escape Rope to escape. It's a crucial item for this specific area.
* No Other Escape Methods: There are no other ways to leave the mansion after you've entered. You can't battle your way out or find hidden exits.
What to do:
1. Reload Your Save: The best option is to reload your save file before entering the mansion and make sure you have the Escape Rope.
2. Find the Escape Rope: Double-check your inventory. You might have accidentally left it behind.
3. Trade with Someone: If you're playing with friends, try trading with someone who has an Escape Rope.
Remember: The Escape Rope is a critical tool for navigating certain areas in Pokemon games. Make sure you always have one handy!