Luna lands at the castle in Canterlot. She darts inside through the doors screaming for Celestia. The Element of magic is still being held by Luna's magic. Looking for her sister the sun is attempting to rise but is failing for that the moon is still in the sky. Gently setting down the mangled crown on the ground Luna puts all her concentration onto the moon so it would make room for the sun. Scooping up the headpiece again, the nighttime ruler starts galloping for the balcony where she would find her older sister raising the sun.
"Sister, I have come with some very important news."
"I know Luna. I have felt a fault in the connection of harmony among ponies." Celestia's eyes are full of worry and fear. "It was in my dream last night that a new terror is rising. One that is ineffective against the elements. It seems though that it has already struck and isn't going to stop until it gets what it wants."
"Tia, turn around and look." Celestia turns around as a gasp exits her mouth at what she sees. Taking the element the yellow magic engulfs the blue taking control over the element. "Luna where did you find this at?" Dropping her head to the ground while debating whether to tell Celestia about Pinkie or not.
"I....I found it laying on the ground of the Everfree. No pony was nearby." A sense of shame was swelling up inside her. 'Thou can not tell Celestia about Pinkie. Something is making her the way she is. ' Her thoughts accidently escape through her lips "Almost as if *gasp* Shadowfrights....it could be a possible solution as to why she was so rude, or maybe it was something else? " Celestia gives her sister a very confused glance then demanding her to explain what she just said. "I should probably get some rest now. " Turning around and dashing off to her room. Leaving behind a very angered sun princess that now has to figure out what her sister said by herself.
"Luna! What the buck! Why can't you tell me what's going on?" Shouting back at her sister who already ran into her room. Thinking on how to get this info from Luna an idea pops into Celestia's mind. 'A mind reading spell is perfect than I will be capable of knowing the info without her actually talking.' Calling upon her spell book she searches for the spell and finds it.
'From mind to mind
and secret to secret
Let the untold be heard by another'
As this was said Celestia's magic worked itself. Yellow aura granting what she thought she wanted. What wasn't read was the small text saying:
Warning: Please be in the same room as the one you want to read. If not, switching bodies is possible.
That's exactly what happened since Luna was in her room. Not in the same room as Celestia.