Who buried Moshe?

Summary: According to Ibn Janach, Moshe, via a miracle. Then he retracts to say that it was Hashem.

Post: Towards the end of Zot HaBracha, we read:

ו  וַיִּקְבֹּר אֹתוֹ בַגַּי בְּאֶרֶץ מוֹאָב, מוּל בֵּית פְּעוֹר; וְלֹא-יָדַע אִישׁ אֶת-קְבֻרָתוֹ, עַד הַיּוֹם הַזֶּה.

6 And he was buried in the valley in the land of Moab over against Beth-peor; and no man knoweth of his sepulchre unto this day.

While this translation renders וַיִּקְבֹּר as if it were passive, a straightforward reading it that is is an active verb. There was someone who buried Moshe in the valley. Who was this?

According to Ibn Janach:

"and he buried him in the valley -- that is to say, he {=Moshe} buried himself in the valley. (And this is possible, that Moshe said to the earth, in the name of Hashem, to open and gather him it, and it opened by the word of God. (And this is the position of Rabbi Yishmael in the Sifrei, parashat Nazir -- the insight of Shadal.) And once he entered in it, he commanded, by the word of God, and it was closed for him after his soul ascended. And this sevara was close to me with nothing holding it back, until I saw the words of the men of the Mishnah (Sotah 1:9), and I turned from my position to their position. (Sefer haShorashim, 52)"

The Mishnah in Sotah reads:

מי לנו גדול ממשה, שלא נתעסק בו אלא הקדוש ברוך הוא, שנאמר "ויקבור אותו בגיא . . . מול . . ." (דברים לד,ו).  ולא על משה בלבד אמרו, אלא על כל הצדיקים, שהמקום אוספם, שנאמר "והלך לפניך צדקך, כבוד ה' יאספך" (ישעיהו נח,ח). ש

Thus, the competing theory that Ibn Janach eventually adopts is that Hashem buried Moshe.

I am not sure where Shadal wrote his haarah that Ibn Janach's former position was actually a Tannaitic position, but I wonder whether Ibn Janach would have been so quick to retract.

What about Shadal? How does he hold:

 ויקבור וגו ': כלו ' נקבר ברצון ה ' דרך נס בלא קובר.

"That is to say, he was buried by the will of Hashem, in a miraculous manner, without a burier."

This would seem to be like the second position. I should note that simply saying that vayikbor has an implicit hakover, like other instances like vayageid, with an implicit hamagid, is presumably ruled out, not just by the slight grammatical irregularity, which is certainly surmountable, but by the end of the pasuk, וְלֹא-יָדַע אִישׁ אֶת-קְבֻרָתוֹ, עַד הַיּוֹם הַזֶּה. If written even in the time of Yehoshua, then there would not have been a human kover. If written much much later, then it could be a statement in retrospect, that they buried him, but just where is lost to us nowadays. But that is theologically very difficult to say, and so Ibn Janach and Shadal are not offering that explanation.

(See also Abarbanel on this.)