Secret recording screen

Please help me understand.

yesterday I saw that there was an ongoing video recording call on my IPhone. I tried to close that window but it wouldn’t close. I double clicked on the centre button to close all open windows. The screen on the particular window was black apart from a small symbol into right hand corner. Unfortunately I didn’t print the screen as I panicked and turned the phone off. Nothing has happened since I turned it on again but now I am afraid of logging into thing such as bank etc if some spy app is recording what I do.

has anyone else had a similar experience?