Perhaps it was too painful for Barnabas to see his little sister's room again. Maybe he didn't even want Willie in there. He'd often become angry when Willie or Julia would dare even mention her name in his presence. Maybe he kept it locked up?
If I were writing the story, I wouldn't want Sarah to show up in the room in which she died. That would imply that she was trapped there forever and that's just too sad to contemplate. Better to find her playing with her ball out in the gardens. That scenario implies hope.And yes, I agree with PennyDreadful. Barnabas would surely have kept that room safely locked. Even more so than Josette's room, Sarah's would have been too sacred a place for mere mortals to disturb.
Judging from 1795, I just don't seem to remember Barnabas and Sara being very close. I mean, Josette was his entire life, he was completely devoted to her. After that it was Jeremiah, his best friend, and then probably his mother. Sara seemed to rank only above Abigail and Joshua.
[spoiler]Actually, the main family had moved to Collinwood by Sara's death. (Remember Barnabas wasn't cursed until after they had all left.) She died from pneumonia from going to the Mausoleum to find vampire Barnabas but instead getting caught in the rain. Thus, she died in the main house. I believe Barnabas was very close to his sister.[/spoiler]
Actually, from watching 1795 I was under the impression Barnabas absolutely adored Sarah. He was devastated when she died.
He almost seemed more like her father than Joshua did. I felt that Joshua was probably more uncomfortable with his young daughter and didn't quite know how to react towards her and it was this void which brought Sarah and Barnabas much closer.
I just think it would have been interesting to see how it would have played out had Barnabas restored the child's room too.It would have made an interesting story plot had they thought to do that before we knew who Sarah was.