Our Mishnah, according to the Rivan and others, who learn it as a case of a Tainas Chiyuv, where the Shomer admits the Pikadon was stolen through his own negligence, could only go according to the Bach, and not the Ketzos.
The Bach holds that even where there is a Tainas Chiyuv (for e.g. "Pashati" for a Shomer Chinam), the Shomer must still say "Hareini Mishalem" before the Baal is willing to be Makneh the Keifel. The Ketzos holds that it's enough to admit Chiyuv for the Baal to be Makneh the Keifel.
If our Mishnah is a case of a Tainas Chiyuv, i.e. "Pashati", then according to the Ketzos, we would expect it to read identical to the language of R'Papa on 34a, where he says, "A Shomer Chinam, once he says, 'Pashati', (the Baal) is Makneh him the Keifel."
We would not need to be taught the word, "V'Shelem", whether it implies actual payment, or even just "Hareini Mishalem" - it should be enough to admit Chiyuv for the Baal to be Makneh the Keifel.
The word "V'Shelem" (and the ensuing discussion whether the word in the Mishnah means Shelem Mamash, or if "Hareini Mishalem" is sufficient) is only appropriate to the Bach, who holds that in addition to an admission of Chiyuv, the Shomer must still demonstrate a willingness to pay (either through actual payment, or by saying "Hareini Mishalem").
Presumably, the Ketzos would have to learn the Mishnah K'Pshuto, as a case of a Tainas Ptur (Nigneveh without Pshia) - similar to how he interprets the Beraisa of "HaSocher Parah M'Chaveiro" on 34a, as a case of Shomer Sachar claiming it was stolen through an Oness - and that explains the reason for the word "V'Shelem" (and the ensuing discussion whether "Hareini Mishalem" is sufficient). Because the Baal will only be Makneh the Keifel immediately upon an admission of Chiyuv, but if your claim is one of Ptur, you must pay, or at least express "Hareini Mishalem" before you get the Keifel.
Does that follow?
Rashi (DH v'Lo) learns the Mishnah k'Peshuto -- as a case of Ta'anas Petur, so the Ketzos is fine according to Rashi. And according to Rashi's son-in-law, the Rivan, the Ketzos himself writes initially that it seems that the owners do not give Kefel merely through the Shomer's admission to a Ta'anas Chiyuv. However, the Ketzos then explains his position according to Tosfos (34a, DH Ela).
Kol TUv,
Dovid Bloom
Thank you, R'Dovid for this prompt reply.
When I initially sent along my thoughts, I had not seen the Ketzos inside, I was only familiar with his Shita, and was therefore happy to see that he addresses how his Shita can coexist with Rivan's Pshat in our Mishnah.
However, L'Aniyas Daati, I cannot understand how it's possible to use Tosfos d.h. "Ela" (34a) to reconcile the Ketzos' Shita with the Rivan.
Below is how I understood the Ketzos and my problem with his answer - maybe you can show me where I'm offtrack.
The Ketzos says - although Lifee the Rivan, our Mishnah is a case where the Shomer made a Tainas Chiyuv ("Nigneveh B"Pshia"), which according to MY opinion is sufficient already for the Baal to be Makneh him the Keifel, and we should not expect the Mishnah to reference him having to pay ("Shelem') or even say "Hareini" - like the Bach holds - Tosfos has already justified for us the existence of the word "Shelem" in the Mishnah, based on the context of the case.
Tosfos explains that our case, as interpreted by Abaye and Rava in Bava Kamma (108a), is where the Shomer swore first, and then paid.
(According to the Rivan, it would be understood as the Shomer first having sworn "Nigneveh" without Pshia, and then admitting afterwards he was really Chayiv for having been Poshea).
Rava holds he has to pay right away to get the Keifel; "Hareini" no longer works, and according to Abaye, even if he paid afterwards, the Baal will still not be Makneh the Keifel, since the Shomer swore first.
That is the only reason why the word "Shelem" exists in the Mishnah, answers the Ketzos. Like Tosfos says: "Shelem" is only there to teach Chiddushei Dinim within the opinions of Abaye and Rava, in a scenario where the Shomer swore first. But in a regular scenario, where he just admitted Chiyuv, does not have to also indicate a willingness to pay, i.e. like the Bach holds.
The problem with the Ketzos' answer is the following:
Tosfos' explanation, that Abaye and Rava understand the word "Shelem" in the unique case of our Mishnah (which, according to the Rivan, is when he swore first and admitted Chiyuv afterwards), to be L'Afukay the Shomer being able to proceed as usual and say "Hareini", implicitly assumes that "Hareini" plays a factor in a regular case (which, according to the Rivan would be when the Shomer just admitted "Nigneveh B'Pshia", without having sworn first).
But according to the Ketzos, there's no need to say "Hareini" when the Shomer admits Chiyuv!
In other words, Tosfos' explanation of the Chiddushei Dinim of Abaye and Rava (that "Hareini" no longer works when the Shomer swore first), in the context of the Rivan's Ukimta in our Mishnah (that the Shomer admitted Chiyuv), implies that Abaye and Rava both hold in a Stam case (according to the Rivan, this would be where the Shomer just admitted "Nigneveh B'Pshia", without having sworn first), that "Hareini" does work to get the Keifel!
Tosfos' explanation seems to be more in line with the Bach's Shita than with the Ketzos'!
B'Chavod.
The Ketzos 295:1 will learn that the Mishnah only says "Shilem" because it is referring to a scenario where the Shomer swore first. In such a scenario Tosfos 34a end DH Ela writes that it is not sufficient to say Hareini Meshalem. However in a scenario where the Shomer did not swear first, it goes down 2 steps. Here not only do we not require Shilem; we also do not require Hareini Shilem because Pashati alone is sufficient.
Chodesh Tov
Dovid Bloom