Translate:
Sara always used to lose her keys.
Is it?
Sara siempre se le perdia los papeles.
Almost. The difference is keys = las llaves vs the papers = los papeles.
A Sara siempre se le perdÃan las llaves.
This is the passive transferring the blame to the keys and not Sara! (Unplanned occurences) So literally it says "the keys always used to get lost with respect to Sara.
Sra