The suspension of disbelief required for these short little films varies. For instance, for this film: Having one’s clothes stolen while in the shower is a bit of a classic prank. So in that sense, it is not that hard to believe that teenage (or close to teenage) girls would do that to one another. So that in itself is easy to believe. But there are elements here that are harder.
For instance, the shower curtain is open, but Stephanie does not see the girls coming in. Now, given the noise, it is understandable that she did not hear them. And actually, if she were to the point where she was washing her face and hair, her eyes would be full of water and she would not see them either. So while having the curtain open is a bit unusual, it does not necessarily mean she would have seen them. Heck, even with it closed, she could have seen shadows and such if she were really paying attention. Of course, this story only works if she is not paying attention.
Another little poetic license is the show house concept, because otherwise one could surmise that she could find other things to cover up with. Given where this was shot, the actuality was that the drawers really were empty, so perhaps that is a draw.
What is lovely in this is the little flourish Stephanie gives when she picks up the note, uses it to cover up, then spins with it. It is rather delightful to watch, actually.
Here are some lovely pictures from this video (direct link here):