What is the ruling on seeking replacement for an item bought that requires possession if it is met in another town?

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If one purchases an item requiring possession and encounters it in another town, he is not entitled to demand it or take a substitute for it, even if both parties agree, because it is an unpossessed sold item. However, if the item is one that does not require possession, taking a substitute is permissible. If the transaction was a Salam contract, taking a substitute is not permitted because the item in a Salam contract is also prohibited from being sold before possession.