Bava Batra 85A

כליו של אדם קונה לו בכל מקום, חוץ מרשות הרבים. ורבי יוחנן ורבי שמעון בן לקיש דאמרי תרוייהו: אפילו ברשות הרבים.

A person’s vessels effect acquisition of any item placed inside them for him, in any place in which they are situated, except for the public domain. And R' Yoḥanan and R' Shimon ben Lakish both say: Even in the public domain, one’s vessels effect acquisition of items placed in them.

אמר רב פפא: לא פליגי; כאן ברשות הרבים, כאן בסימטא. ואמאי קרו לה רשות הרבים? שאין רשות היחיד.

Rav Pappa said: These amora’im do not disagree: Here, when Rav and Shmuel state that one’s vessel does not effect acquisition for him, they are speaking of a vessel placed in the public domain; there, when R' Yoḥanan and Reish Lakish state that his vessel effects acquisition on his behalf, they are referring to a vessel located in an alleyway. And why do they call an alleyway the public domain? The reason is that an alleyway is not a private domain.

הכי נמי מסתברא, דאמר רבי אבהו אמר רבי יוחנן: כליו של אדם קונה לו בכל מקום שיש לו רשות להניחו. יש לו רשות ⁠– אין, אין לו רשות ⁠– לא. שמע מינה.

The Talmud points out: So, too, it is reasonable to interpret R' Yoḥanan’s statement in this manner, as R' Abbahu says that R' Yoḥanan says: A person’s vessels effect acquisition for him in any place where he has permission to keep them. It can be inferred from here: In a location where he has permission to keep them, yes, his vessels effect acquisition for him. But in a place where he does not have permission to keep his vessels, they do not effect acquisition for him, and one has permission to keep his vessels in an alleyway but not in the public domain. The Talmud affirms: Conclude from this statement that when R' Yoḥanan referred to the public domain he meant an alleyway.