Dive under the desk!

Panicking, Anna immediately crouched down and squeezed under the desk, the rapid movement causing several more "clicks" to be heard coming from her skirt, which was about 1/3 the way open at this point. Not 5 seconds after she got into position, one of the female coaches with dark brown hair stepped into the office and began looking around.

"Let's see...where was that form..." The sound of several drawers opening could be heard from Anna's position. The girl remained completely still during this time, holding her breath so not even the sound of her breathing would escape. The cold feeling of the hardwood floor pressed up against Anna's bare bottom, only serving to add another distraction. "Ah, there you are!" The coach exclaimed, taking out a piece of paper and slamming the drawer shut, opening the office door once more and heading back to the gym.

Breathing a sigh of relief, Anna steps out from under the desk and into the locker room, checking her phone once more.

"Nice job. Now, go to locker number 55 and open it up. You will find her shirt, skirt and bra inside. Take them and put them inside locker 23, I will recover them later. Include the shirt and skirt, and you'll get a bonus reward."

Walking down the long aisle of lockers, Anna finally found the correct one; 55. Using the master key, she opens the locker to find exactly as the message said; a shirt and skirt that looked exactly like Anna's, and a lacy pink bra that sat on the top shelf. Taking the bra first, being the primary objective, Anna stuffs it into her skirt pocket and turns back for the rest. However...another message arrived from the mysterious person;

"Someone's coming!"