http://spanish.stackexchange.com/questions/1079/se-pronoun-in-no-fault-constructions In above site, it has written about the "accusative pronoun":
example: Se me cayó.
This element "me" is used to "accuse" somebody of being "guilty" of that.
another examples:
Se me cayó el libro.
Se te perdió la mochicla.
Now see what is written in another site about "Se with Unplanned Occurrences" or "The accidental reflexive construction": http://www.elearnspanishlanguage.com/grammar/verb/accidentalreflexive.html
The accidental reflexive construction indicates that the action was unintentional. In addition, because the subject is only referred to by an indirect object pronoun, this construction gives the sense that the subject is not to blame - he or she had nothing to do with the accident.
examples:
Se le cayó la pluma.
¿Se te perdieron las llaves?
Now I confused which is correct? According to first site information I understood that Indirect object pronoun is used to "accuse" somebody of being "guilty" of doing action. So I conclude the action of that one is intentionally and not accidentally. According to second site the action is done accidentally. which one is correct? Maybe,I should say indirect object pronoun in passive se construction indicates somebody that is guilty of doing an action accidentally???