I find this scenario hard to believe. There are so many red flags about your particular story that I find what you say as a suspicious story.
First of all: Hospitals KNOW about HIPAA laws and would never label a room revealing Plan B patients. I have never known a hospital to take information from patents behind a curtain. So weird because anyone can hear through a curtain as there is zero expectation of privacy through fabric.
Secondly: Plan B pills are available at CVS, WalMart, Walgreens and other drug stores, over the counter. Hospitals cannot be bothered with administering a pill that is sold over the counter, like aspirin and Neosporin cream. Besides which, whenever I was in the hospital and needed to swallow medication, the nurse showed up with the pill and a cup of water. Your story about going out into the hallway for water is just not standard operating procedure.
Also, let's pretend that the pretend sign on the door was not there and this lady who knows your mum did see you. What would you have told your mum as to why you were in the hospital? You would have had to lie, I guess. Oh well.
There are too many holes in your little scenario here, so I call a troll.