I was thinking about the answer of Rav Shach in terms of the Raavad who makes a distinction between a pledge and a deposit (as it relates to the law of, "Here it is")]. Clearly Rav Shach does not want to take the path that the both are not owned by the person who has the object because according to R. Isaac the pledge is owned by the lender just like the deposit is owned by the depositor. So Rav Shach makes a distinction between when the time of the obligation starts, the time he receives the deposit or the time some accident occurs to it. I am not sure what Rav Shach intends here. However, I think there is a much clearer distinction. For a deposit, the time to give it back is exactly when the depositor asks for it back. (This would apply to both an unpaid and a paid guard. But Rav Shach might be referring to a borrower. However, the time to give back the pledge to the borrower is when the borrower pays back the debt, not when he asks for it back. So, when the borrower gives the pledge that is not immediately here is your money paid in full. Rather when he pays back the money, that is when the debt is paid back.---------------------------------------------I was thinking about the answer of רב שך in terms of the ראב''ד who makes a distinction between a pledge and a deposit (as it relates to the law of, "Here it is")]. Clearly רב שך does not want to take the path that the both are not owned by the person who has the object because according to ר' יצחק the pledge is owned by the lender just like the deposit is owned by the depositor. So רב שך makes a distinction between when the time of the obligation starts, the time he receives the deposit or the time some accident occurs to it. I am not sure what רב שך intends here. However, I think there is a much clearer distinction. For a deposit, the time to give it back is exactly when the depositor asks for it back. (This would apply to both an unpaid and a paid guard. But רב שך might be referring to a שואל איפה שיש חילוק הזה. However, the time to give back the pledge to the לווה is when the לווה pays back the debt, not when he asks for it back. So, when the לווה gives the pledge that is not immediately, "Here is your money paid in full." Rather, when he pays back the money, that is when the debt is paid back.