I agree with @gustavson but will write a simpler answer for anyone who might benefit.
Let's say we are just coming home from visiting Aunt Leticia who lives an hour away. We discover we are without house keys because they got left behind at Aunt Leticia's house. Let's write a passive sentence:
Las llaves se olvidaron allá, en casa de mi Tía Leticia.
Now we get to be a bit picturesque because Spanish allows us to do this, and we will add an indirect object that shows whom this terrible thing happened to:
Las llaves se nos olvidaron en casa de mi Tía Leticia.
A common variant of this is
Las llaves se nos quedaron en casa de mi Tía Leticia. | The keys got left behind at Aunt Leticia's house [and that affected US].
The implication is that we are the dummies that made the boo-boo, or the poor idiots who had the bad luck.
As Gustavson pointed out, this construction is similar to
Se me cayó el lápiz. | The pencil fell [which affected ME].
Here's a similar construction in English:
And then she up and died on me.
Although this has some differences from the llaves construction, it's a nice example of how the person affected can show up in a picturesque expression.
Turning now to your Question 2:
Is the usage the same as this?
Se lo dice/dicen que ... (It is said that ...)
It would be the same, I guess, except that "Se lo dice" doesn't work. "It is said" would be expressed in Spanish as
Se dice que ...