Missing domains in InfluxDb

I have a simple InfluxDb setup:

influxdb:
  host: myhost
  measurement_attr: entity_id

measurement_attr: entity_id is there so that my temperature sensors get logged with the entity name as key rather than “C” (which I don’t understand why it would be the default)

It has all been working fine until today when I realized that one of my domains is not there. Can it be because apparently these entities have no id?

This is how my “water_heater.radiators_water” entity looks like:

<template TemplateState(<state water_heater.radiators_water=unknown; min_temp=10, max_temp=60, current_temperature=50, temperature=48, target_temp_high=None, target_temp_low=None, friendly_name=Domestic Hot Water, supported_features=1 @ 2021-01-14T09:20:17.544559+00:00>)