How is your coordinator linked to your home assistant?
For example if you use Zigbee2MQTT and you have either Zigbee2MQTT or Homeassistant pointing to the internal ip of mosquito (192.168.1.11 for example) and your router goes down (with dhcp), it’s possible it cannot communicate anymore.
This isn’t the case if it’s all running on the same box using localhost as address, running it in a docker network or when you run ZHA however.
that uses mDNS, which in some cases requires your router to be online to be able to resolve it to a ip. If part of your internet disruption was your router going down, it would explain the issue