I was learning recently the sugya of heilach in Bava Metzia and was bothered by something. The Gemara on the top of 4b brings a machlokes tannaim. One of those shitas is Rabbi Akiva who holds (in the case of a shtar that only says Selaim or Dinarim) that if lender says 5 and the borrower admits to 3, he is patur because it is k'mashiv aveidah. Why? Well what is the din Mesheiv Aveidah. The Chachamim said if Reuven finds Shimon's wallet with 100, and Shimon claims it had 200- Reuven is patur from his torah Shevuah of Modeh B'miksatz. The reason being Tikkun Olam that people will not want to return lost objects for fear of having to make a shevuah.

My question is as follows:

Nu, what's this k'mashiv aveidah? Ask punct on meshiv aveidah. It's heilach mamish. Person A gives Person B 3 of whatever that he found of Person B, Person B says there should have been 5. Says the Chachamim that if not for us, Person A would be chiyuv a shevuah. Why? It's heilach. Therefore, Heilach is chiyuv.

My chavrusa and I were forced to say that the case is if Person A still has the aveida wallet in his house, and person B gives simanim, then after giving the simanim, says that there is 200 in the wallet, etc. If it is a pikadon only then I think at least to Rashi its heilach automatically. Also, money being only heilach in Beis Din to Rashi might be davka by a loan that the money currency isn't expected to be returned, rather the value. Yet, if one finds a wallet, he is allowed to use the money in it- just needs to return the value? I don't think that is true. L'maaseh, to us, that was quite an odd takana if something like we thought was the case. Because anyway, just tell the guy to just bring whatever he says he found to Beis Din, and its heilach. And to Rav Sheishis, he's patur. Unless, one were to say the halacha is heilach is chiyuv...but I don't believe that is what most Rishonim hold.

Any mekors that Kollel knows that discusses the topic? I looked around a little and could not find anything.

Avraham Serbin, Far Rockaway, NY USA