Well, that happened.

Rainbow had decided to attempt teleportation to Sweet Apple Acres.  Surprisingly, it actually worked.  She ran into Aj's house just as Aj was about to leave.

"What in tarna,"Aj had said before being interrupted by RD.

"No time to explain just follow me to Twilight's," RD had said.

"Rainbow, why do ya have a horn?"

"I could ask you the same thing."

at that moment RD pulled out a mirror emergency mirror she got from Pinkie before she left out of her hair and levitated it in front of AJ.

"Before you ask why you have a horn or how I am somehow levitating this mirror with my horn when I just recently got it we need to get to Twilight's and head to Sugarcube Corner."

"Good idea we can figure out what happened once we're together, what about Rarity and Flutters?"

"Pinkie Fly is getting them.  You probably understand that pun already."

"Eeyup."

They finally arrived at Twilight's and heard a scream coming from inside.  "Guess she found out about her horn, or lack-there-of," RD had said.

"Why do ya say she lost her horn," Aj asked.

"Because out of me, you, Twilight, Fluttershy, Pinkie, and Rarity, we had 2 unicorns, 2 earth ponies, and 2 pegasi.  we became the 2 unicorns so she had to have lost her horn.  Uugggh, I'm getting all egghead-y," RD replied.

The 2 unicorns went into the ex-unicorn's house and AJ just yelled "Twi, meet us over at Sugarcube Corner!  We have somthing important to tell ya!"

Before Twilight could look down and respond they had (successfully) teleported themselves into SCC.  She then walked down the steps and ran to Sugarcube Corner hoping nopony noticed she had lost her horn.  Losing her horn was enough, but not even getting wings instead really annoyed her.