Unknown access to microphone

An app accessed my microphone and my phone wasn’t in use! I literally picked the phone and then immediately saw the orange bubble light go off.

I have restricted access to my microphone so it asks every time. I find this particularly worrying.

I saw there was someone else who had a similar issue posted in November 2020. But there was not an appropriate response. I had no apps opened. I wasn’t using my phone. I picked it up only to find the orange bubble disappear.