For debugging purposes, ChirpStack keeps a log of the last LoRaWAN frames that are exposed through the available integrations. This feature is available both for gateways as devices.
The LoRaWAN frames tab on the gateway detail page will display all frames sent and received by the selected gateway. This includes frames received from unknown devices.
The LoRaWAN frames tab on the device detail page will display all frames which have been authenticated with the (session)keys of the device. This means that in case your device is experiencing MIC calculation issues, you will see the uplink frame under the gateway frame logs, but not under the device frame logs.