Rabbi Chiyya bar Abba said in the name of Rabbi Yochanan: one who falsely pleads that a thief took a lost object that he had found pays the double payment. What is the reason? "For any lost thing of which one says" (Exodus 22:8). They raised an objection against him: "When a man gives" (Exodus 22:6) — the giving of a minor is nothing. And I have only the case where he gave it to him while he was a minor and claimed it from him while he was a minor; from where do I include where he gave it while a minor and claimed it after he had grown up? The verse states "the matter of them both shall come before the judges (the Elohim)" — meaning the giving and the claiming must be as one. And if it were so [that a found object incurs liability like a deposit], let it be like a lost object [which does not require a valid act of giving]. With what are we dealing here? Where he consumed it while he was a minor. Rav Ashi said: they are not comparable. A lost object comes into one's hand through the power of a person of legal competence [the finder], whereas this [a deposit given by a minor] does not come through the power of a person of legal competence.
The Finder Who Falsely Claims a Thief Took the Lost Object
Yalkut Shimoni on Torah 346:11
אֲמַר רַבִּי חִיָּא בַּר אַבָּא אֲמַר רַבִּי יוֹחָנָן, הַטּוֹעֵן טַעֲנַת גַּנָּב בַּאֲבֵדָה מְשַׁלֵּם תַּשְׁלוּמֵי כֵּפֶל. מַאי טַעְמָא, עַל כָּל אֲבֵדָה אֲשֶׁר יֹאמַר. אֵיתִיבֵיהּ, כִּי יִתֵּן אִישׁ, אֵין נְתִינַת קָטָן כְּלוּם, וְאֵין לִי אֶלָּא שֶׁנְּתָנוֹ כְּשֶׁהוּא קָטָן וּתְבָעוֹ כְּשֶׁהוּא קָטָן, נְתָנוֹ כְּשֶׁהוּא קָטָן וּתְבָעוֹ כְּשֶׁהוּא גָּדוֹל מִנַּיִן, תַּלְמוּד לוֹמַר עַד הָאֱלֹהִים יָבֹא דְּבַר שְׁנֵיהֶם, עַד שֶׁתְּהֵא נְתִינָה וּתְבִיעָה כְּאֶחָד, וְאִם אִיתָא, תֶּהֱוֵי כַּאֲבֵדָה. הָכָא בְּמַאי עַסְקִינַן, שֶׁאֲכָלוֹ כְּשֶׁהוּא קָטָן. רַב אַשִּׁי אֲמַר לָא דָמְיָא, אֲבֵדָה אָתְיָא מִכֹּחַ בֶּן דַּעַת, וְהָא לָא אָתֵי מִכֹּחַ בֶּן דָּעַת.