Translation:In the accident, the lawyer lost the nail.
I'm not sure what this is trying to say in Portuguese, but in English, it sounds like she lost a specific nail that had been in her possession; in context, it sounds like a nail she was carrying as a piece of evidence, perhaps. If the accident caused her to lose one of her own nails, it should be 'the lawyer lost a nail'.
In English, you would only say it the way Duo has it if you had already been talking about the lost fingernail and were explaining how it was lost, in which case, the two clauses would only ever be expressed in the reverse order: "The lawyer lost her nail in the accident." The English sentence would never be said by anyone ever in the order given.