הובלתי כתיב in Midrash Rabba on Noach

Summary: Midrash Rabba and Tanchuma appear to have a derasha based on a ketiv which isn't.

Post: In Midrash Rabba on parashat Noach, we encounter the following midrash, which plays on a pasuk in Yechezkel 31:15:

טו  כֹּה-אָמַר אֲדֹנָי יְהוִה, בְּיוֹם רִדְתּוֹ שְׁאוֹלָה הֶאֱבַלְתִּי כִּסֵּתִי עָלָיו אֶת-תְּהוֹם, וָאֶמְנַע נַהֲרוֹתֶיהָ, וַיִּכָּלְאוּ מַיִם רַבִּים; וָאַקְדִּר עָלָיו לְבָנוֹן, וְכָל-עֲצֵי הַשָּׂדֶה עָלָיו עֻלְפֶּה.

15 Thus saith the Lord GOD: In the day when he went down to the nether-world I caused the deep to mourn and cover itself for him, and I restrained the rivers thereof, and the great waters were stayed; and I caused Lebanon to mourn for him, and all the trees of the field fainted for him.

The midrash reads:

אמר רבי לוי: משל את הצדיקים בדירתן ואת הרשעים בדירתן. 
את הצדיקים בדירתן, שנאמר: (יחזקאל לד) במרעה טוב ארעה אותם ובהרי מרום ישראל יהיה נויהם. ואת הרשעים בדירתן, (שם לא) כה אמר ה' אלהים ביום רדתו שאולה, האבלתי כסיתי עליו את התהום. 
ר"י בר רבי אמר:הובלתי כתיב:, אין עושין כסוי לגיגית, לא של כסף, ולא של זהב, ולא של נחושת, אלא חרס לאותם שהם ממינה. 
כך, רשעים חשך גיהינום, חשך תהום. 
חשך הובלתי רשעים לגיהינום, וכסיתי עליהם את התהום, חשך יכסה חשך

Rabbi Yehuda bar Rabbi says הובלתי is written.

The 'problem' is that in our texts, הֶאֱבַלְתִּי, with an aleph, is written. Vetus Testamentum records one instance of it spelled like this in this pasuk:

Here is what Tirosh, a commentator on Midrash Rabba, has to say:

He notes the issue, and cites himself in his Mesillot, and that so is the girsa as well in Shemot Rabba perek 14. But in Vayikra Rabba perek 27 and Bemidbar Rabba perek 1, these two words do not appear. (I would add that it does appear in Midrash Tanchuma.) He suggests that it is a scribal error via a copying from later on in the midrash, where it states הובלתי רשעים לגיהינום. But even if we assert that it is from the primary language of the midrash, it is fairly straightforward to realize that this is not the intent, that it is so written in the Scriptures. Rather, since the language of הֶאֱבַלְתִּי is not really understandable in this context of the melitza, as all the pashtanim have difficulty with it, the entire construction is the pattern of hiphil based on the root אבל, which is strange and has no fellow except for one in Eicha 2:8, where it implies destruction. Therefore they darshened it as if it were written הובלתי.

Buber writes similarly on Tanchuma, saying that it is darshened 'as if' it were written הובלתי.

I think this is somewhat plausible in this context.