Stanford finally returned to his home dimension and was content to see everything looked exactly as it was before he was pushed in- Granted, it is much cleaner and the piles of research he had arranged on the walls and any other surface was messed up but at least it wasn't turned into...some Stan Mystery Shack or something. Stanford chuckled at the silly idea.
He didn't really understand why the familiarity of his lab and home made him uncomfortable-
Then he saw it.
Mabel had been running around, being creative and happened to grab one of Ford's many books for reference. When she put it back all tilted and on the place it had not been previously (someone had arranged them by alphabetical order of the title- it annoyed Ford a little as he would have done it by writer), Stanley seemed to be summoned out of no where and put the book in his rightful place.
The uncomfortable feeling returned and Stanford finally understood why.
Thirty years. Thirty years living here and the place wasn't lived in.
(Or: Stanley never really changed anything about Ford's lab, always believing he'd come back and afraid to mess things further)