But is it?
R. Yehiel replied: It is a legal presumption that all agent carries out his mission.
R. Nahman ruled: In [respect of a law] of the Torah, there is no legal presumption that an agent carries out his mission; in [respect of a law] of the Scribes there is a legal presumption that an agent carries out his mission.
R. Shesheth, however, ruled: In respect of the one as in that of the other there is a legal presumption that an agent carries out his mission
What follows is an extensive attempt to show examples of Torah laws in which the presumption of an agent’s success is a given. The problem is, the examples are all of Beit Din or Priests or individual rabbis (chaver) carrying out their duty.
There [the presumption is justified] for the reason stated: Because it is known that Beit Din would not shirk their duty.
The same holds true for the others. So it is hard to demonstrate that an ordinary agent would be presumed to have carried out the responsibilities for a Torah law, as opposed to a Rabbinic ordinance.
On a different subject, there is a remarkable and rare aside on this page. In a discussion of a fine point of law, and a well-argued point, there is this parenthetical:
(But did not they themselves explain [their difficulty] thereby? — In fact it was this that they said to him: ‘Did you embody it in the Gemara?)
A statement which seems to be an early stage of addition to what will become the Talmud – the question being asked is, ‘has this excellent point been added to the commentary?’ It is a glimpse into the process by which the rabbis decide what will be in the text and what will not.