The OSI model provides the path for the data transmission process from one point to the other. In essence, the transmission process traverses the seven layers consecutively while the integrity of the packet or the datagram is maintained. Initially, the packet is assigned a logical address which is usually an IP address. This is important for the router to filter out desired and undesired packets using their header addresses before routing them to their destinations.
Addressing is simply like the normal postal addressing of letters to make them more secure and also get delivery feedback. In the process of packet transportation, it is usually encapsulated, which means wrapping with important information containing protocols at each OSI layer model. There is no alteration of the data itself, but in the process of transmission, the data which was turned into segments and then packets are only assigned logical addresses in their headers for identification since several packets of data are transmitted in the channel. At the other end of the channel, which is the destination of the packet, de-capsulation is done, and the original packet is retrieved and converted back to frames and then data.
The reason why there is no loss of data is basically because of the logical addressing that helps in the identification process and re-building of the data at the destination. The encapsulation process at the start of transmission in the OSI model also ensures that the packet has the relevant protocols that will enable it to pass through the layers successfully without losing its integrity despite being broken down into small segments.