I seem to recall something similar happening to a A330 belonging to a British charter airline a few years back?
IIRC They had had a hard landing which cracked part of the main gear structure, I think the crew reported the hard landing and the onboard QAR recorded it also. Nothing was found during the required maintenance checks however, on the next departure, the gear failed to retract and so they returned at which point the damage was found following a further inspection.