When and how does Hermione end up naked?

Alone Time in the Prefect's bathroom

During Lunchtime, Eighth year Hermione Granger takes the opportuinty in the Prefect's bathroom for some alone time. The reason for the alone time so she can't think of Harry Potter her friend who she wants. Hermione lets her school's robe fall so she unbutton her blouse revealing her School bikini top which was her house colors, she pulled down her skirt to show her bikini bottom showing her nice ass which Hermione knows Harry likes to looked at. Hermione turned on the Faucet when it was full she got into the bath.

For an few minutes....

Hermione was feeling good about herself, Unwared she was being watch, while she was enjoying herself someone say "Hehe" while grabbing Hermione's robes, the only clue was on the wirst being Green instead of red. Hermione turned around "Huh? somebody there?" She replied. Hermione turned to where her clothing were suppose to be, Hermione shriked "My Clothes! they're gone!". Hermione got out of the bath Curious on what happen to her clothes, " Hello???" Said Hermione. She walked over the room trying to find her clothes while her ass and breast were perky from being wet. "Who could have done this" said Hermione while looking at the Door unawared there's an shadow figure on her left side.