Who is responsible for the loss of the property collection courier?

There are four characters in this question, one is the consumer, that is, the buyer, the other is the merchant, that is, the seller, the other is the property, and the other is the courier company. The relationship between consumers and businesses is a sales contract. Merchants deliver goods to buyers through courier companies, and there is also a contractual relationship between merchants and courier companies. The property company has the fact of collecting express delivery. Collection with collection obligation and collection without collection obligation are related to whether the owner allows the property to be collected by express delivery. If the owner entrusts the property to collect express delivery, the service scope of the property also includes the express delivery signing service for the owner. If so, there will be two consequences. One is that the seller's merchant has delivered the goods purchased by the buyer through the courier company, and completed the responsibility of delivery. At this point, even if the goods are damaged or lost, it has nothing to do with the seller. Another is that at this time, the merchant should take good care of the goods and wait for the owner and the buyer to pick them up. If the buyer finds that the goods are damaged or lost after receiving the goods, he should find a property management company, which will bear the responsibility. If the owner does not entrust the property to collect the courier, then the property company should not help the owner sign and keep the courier. If the owner does not inform the courier company to send the courier to the property, but the courier company will send the courier to the property and the property will sign for it, then it cannot be considered that the owner has received the courier. If the courier is lost or damaged at this time, then the owner also needs to defend the rights of the merchant and ask the seller to replenish the goods for a refund, which has nothing to do with the property company. If the owner temporarily entrusts the property to sign and keep the courier, then when the courier company gives the courier to the property company, it can already be regarded as that the seller has completed the delivery. If the goods are lost or damaged in the process of property preservation, then the property company does not have to bear the responsibility, and neither the seller nor the courier company itself does.