A lightning strike is LOUD like temporary hearing loss loud.
I had a window seat in business class in a 737 and I was leaning against the side kinda glancing outside when a blinding flash occurred and this was as loud as a gunshot without hearing protection.
i had temporary hearing loss in my right ear.
Next day my eardrum was still sore.
So my best guess is in your case a lightning strike occurred in the vicinity of the airplane but didn’t actually hit it.