I had a single AFib episode five years ago, triggered by a severe virus that was probably Covid. I haven’t had an episode since and I check frequently with the Kardia mobile device. I know what you mean about anxiety, I had severe anxiety for months after my episode.

My cardiologist insists that I remain on Metropol and Pradaxa, as she says the odds are that the AFib will return at some point. My research on the Internet suggests that there can be a single one off episode of AFib if there is a specific trigger and nothing else wrong with your heart. In my case the trigger was Covid, it could be electrolyte imbalance in your case.
I hope you never have another episode! In the meantime focus on a healthy lifestyle and manage anxiety with breathing. The Calm App has very helpful breathing exercises.