Indeed, as Tzvi Daum has noted, it would appear that the Targum Yerushalmi quoted by the Abudraham attests to the tradition to which the prayer alludes.
To be sure, our printed editions of the Targum Yerushalmi translate Gen 2:2 with the root "sh-l-m" (meaning completion). However, Abudraham clearly quotes the Targum Yerushalmi as translating "v'hamid". And, indeed, as can be seen on the site of the Comprehensive Aramaic Lexicon (http://cal1.cn.huc.edu/), in manuscript Paris 110 of the Targum Yerushalmi (one of the "Fragment Targum" manuscripts), Gen 2:2 is indeed translated "v'hamid". It would appear that it was to this version that Abudraham was referring.
(It should also be noted that Sperber, in his critical edition of Targum Onkelos, notes a variant of "v'hamid" in Gen 2:2 from an early 16th century printing of Onkelos).
