The Beis Yosef (Orach Chaim § 670) asks the famous question why we celebrate eight days of Chanukah, when there was seemingly only seven days of miracle (the candles being lit the first day was expected). He gives three different answers.
Quite surprisingly, he was preceded by the Tosafos HaRosh (Shabbos 21b s.v. ונעשה נס), who not only asks the same question, but gives the exact same three answers.
As far as I know, the Beis Yosef didn't have access to the Tosafos HaRosh. This would seem then to be a major coincidence.
However, maybe I'm wrong. Maybe he had it, and for some reason doesn't cite him. Does the Beis Yosef ever cite the Tosafos HaRosh explicitly? If not, are there any indications that he had access to it, perhaps other examples of this kind? Do any scholars address this question?