Mishnah Taharos 8:3: If one loses something during the day and finds it that day, it is pure. If [he loses it] during the day and he finds it that night, or at night and he finds it the next day, or that day and finds it the next day, it is impure. This is the rule: Anything which the night, or part of it, passed over it [while it was lost] is impure. If one spread out vessels in a public domain they are pure. If [he did so] in a private domain they are impure, but if he was guarding them they are pure. If they fell [beyond his view] and he went to retrieve them, they are impure. If his bucket fell into the pit of an am ha'aretz, and he [the owner] went to bring something with which to bring it up, it is impure because it was left it in the domain of an am ha'aretz for even one moment. 4

הַמְאַבֵּד בַּיּוֹם וּמָצָא בַיּוֹם, טָהוֹר. בַּיּוֹם וּמָצָא בַלַּיְלָה, בַּלַּיְלָה וּמָצָא בַיּוֹם, בַּיּוֹם וּמָצָא בַיּוֹם שֶׁלְּאַחֲרָיו, טָמֵא. זֶה הַכְּלָל, כֹּל שֶׁיַּעֲבֹר עָלָיו הַלַּיְלָה אוֹ מִקְצָתוֹ, טָמֵא. הַשּׁוֹטֵחַ כֵּלִים, בִּרְשׁוּת הָרַבִּים, טְהוֹרִין. וּבִרְשׁוּת הַיָּחִיד, טְמֵאִין. וְאִם הָיָה מְשַׁמְּרָן, טְהוֹרִים. נָפְלוּ וְהָלַךְ לַהֲבִיאָן, טְמֵאִים. נָפַל דָּלְיוֹ לְתוֹךְ בּוֹרוֹ שֶׁל עַם הָאָרֶץ וְהָלַךְ לְהָבִיא בְמַה יַּעֲלֶנּוּ, טָמֵא, מִפְּנֵי שֶׁהֻנַּח בִּרְשׁוּת עַם הָאָרֶץ שָׁעָה אֶחָת:

Mishnah Taharos 8:4: One who left his house open and finds it open, locked and finds it locked, open and finds it locked, it is pure. If he left it locked and finds it open, Rabbi Meir declares it impure, but the Sages say it is pure because [they assume that] there were robbers who changed their minds and left [without entering the house].

הַמַּנִּיחַ אֶת בֵּיתוֹ פָתוּחַ וּמְצָאוֹ פָתוּחַ, נָעוּל וּמְצָאוֹ נָעוּל, פָּתוּחַ וּמְצָאוֹ נָעוּל, טָהוֹר. נָעוּל וּמְצָאוֹ פָתוּחַ, רַבִּי מֵאִיר מְטַמֵּא, וַחֲכָמִים מְטַהֲרִין, שֶׁהָיוּ גַנָּבִים וְנִמְלְכוּ וְהָלְכוּ לָהֶן: