Greetings, Mariana!
Thanks for your spooky question! I've been in the same situation, so I certainly sympathize.
Unfortunately, if you aren't inside Disneyland Park before the clock strikes noon you may not get a spot in the
virtual queue for
Haunted Mansion Holiday. I'm so sorry, I wish I had better news for you! I would check to see if the virtual queue is still open as soon as you do enter the park, it's possible that the queue won't fill right away. Otherwise, I'm afraid that there really isn't a way to join the queue.
When I have to miss out on something in the parks I usually compensate with a snack. There are some
excellent Halloween treats available, including special Haunted Mansion-themed churros (near the mansion, naturally) and an adorable Monstropolis Float at the
Tropical Hideaway. I know it's not the same as experiencing a ride you love, but it might help!
I hope you still have a frighteningly great day at the parks, Mariana, and that you can visit Jack Skellington another day.
Keep moving forward!
Amanda