Do I write you do not need to rejoin in that message?
After a reset of the RN2483 module you will need to rejoin. However if you saved everything after the last transmit, you can use ABP join which basically initialized the LoRaWAN stack within the module without transmitting/receiving.
If the code on the main controller does not reset the RN module when the main controller is reset you do not need to rejoin. However in a lot of cases the main controller will be reset by removing and reapplying the power of the node and that will reset the RN module as well.