。
Her handbag was stolen.
Literal
She [topic-は] handbag [object-を] was-stolen.
This is the so-called 'adversity passive' or 'suffering passive' — a passive construction where the topic isn't the thing acted upon, but a person affected by what happened. Literally: 'she had her handbag stolen.' The を marks the affected possession even though the verb is passive (盗まれる), a structural quirk specific to this Japanese construction. The pattern conveys that the topic person was inconvenienced or harmed by the event. Compare 私は雨に降られた ('I was rained on,' literally 'I, by the rain, was-fallen-upon') — same structure, no English direct passive equivalent.