My question is, how is rashi Mechayev for the hana'as achila? L'chora he would hold of tosafos' answer of chasar me'at. If so, surely there is no chisaron (even Me'at) in the case if Mashkin and it should be zeh nehne v'ze lo chasar, and therefore patur. (note rashi's change from lo chazya L'BA'ALIM to lo chazya L'MIDI?)
S. Wanderer, London, UK
Tosfos in Bava Kama 20b writes that although one cannot be liable for Geneivah since the item was worthless at the time he swallowed it, it is not considered "Zeh Neheneh v'Zeh Lo Chaser" since the eventual Hana'ah was enabled and made possible by the original Chisaron.