In the famous argument about Tanuro Shel Akhnai (Bava Metzia.59b) R' Eliezer claims to faithfully represent the Heavenly tradition and he's supported by the Heaven. Neither R' Yehoshua, nor God admits that R' Yehoshua's approach is traditional as the Gemmorah testifies:
"בההיא שעתא א"ל קא חייך ואמר נצחוני בני נצחוני בני"
"The Holy One, Blessed be He, smiled and said: My children have triumphed over Me;"
From the fact that God did not respond in the manner He resolved the dispute between the school of Hillel and the school of Shammai: "Both are the words of the living God", I understand that in God's eyes Rabbinic ruling was NOT traditional, in other words, there was no such custom coming down from Moses.
On the other hand, the fact that R"Y did not simply evoke the majority rule but opposed the "Heavenly assertion of R"E's truth" points to his objection to the very approach of following the divine teachings, which I understand as "the tradition".
Do our sources discuss the phenomenon, that when the "Not in Heaven" approach was accepted as a legitimate Halachic approach, the chain of the Mosaic tradition(s) was broken?