Origen, Against Celsus 1.47: 47 .... For in the eighteenth volume of the Judaic Antiquities Josephus testifies to John as having been a baptist and promised cleansing to those who were baptized. But he himself, though not believing in Jesus as Christ, in seeking the cause of the fall of Jerusalem and the destruction of the temple, whereas he ought to have said that the conspiracy against Jesus was the cause of these things happening to the people, since they killed the prophecied Christ, even says, being unwillingly not far from the truth, that these things happened to the Jews to avenge James the Just, who was the brother of Jesus the so-called Christ, for the Jews killed him in spite of his great righteousness [ταῦτα συμβεβηκέναι τοὶς Ἰουδαίοις κατ̓ ἐκδίκησιν Ἰακώβου τοῦ δικαίου, ὃς ἦν ἀδελφὸς Ἰησοῦ τοῦ λεγομένου Χριστοῦ, ἐπειδήπερ δικαιότατον αὐτὸν ὄντα ἀπέκτειναν]. ....
Origen does not claim to be quoting Josephus here. The only citation he gives (which he then paraphrases briefly rather than quoting in any sense) is book 18 of the Antiquities, which we all know lacks anything about James the Just. But he does attribute something about James the Just to Josephus, without using any of the usual lead-ins for direct speech or quotation. The most interesting thing, obviously, is the comparison of his apparent summary or paraphrase of Josephus with Eusebius' quotation of Josephus (the underlined words are the only differences between the two):
Eusebius: ταῦτα δὲ συμβέβηκεν Ἰουδαίοις κατ̓ ἐκδίκησιν Ἰακώβου τοῦ δικαίου, ὃς ἦν ἀδελφὸς Ἰησοῦ τοῦ λεγομένου Χριστοῦ, ἐπειδήπερ δικαιότατον αὐτὸν ὄντα οἱ Ἰουδαῖοι ἀπέκτειναν.
Clearly the two passages are connected. In order to conjure up a lost writing of Josephus in which to mentally place this passage alleged by Eusebius, one would have to suppose that Origen, too, is quoting from this lost writing, and that when he names the exact book (number 18) of the exact work (the Antiquities) he ends up paraphrasing, whereas when he fails even to name the work he ends up quoting pretty much verbatim. One would also have to suppose that Eusebius, contrary to his usual custom, also failed to name the work from which he was quoting, despite quoting it nearly verbatim. All things are possible, but this is a lot to swallow.