This happened about a few days ago, I was watching some videos and had to get up to get something, so locked the screen before going as is my habit, when I came back I had a notification which is why my screen was turned on the lock screen, but my attention went to a duplicate padlock icon on the left of the og lock icon which had a sort of protruding thingy next to it, like a landscape or something, something that would resemble a gallery icon in android, I clicked on it, nothing happened, clicked on it again and it disappeared. I turned on my phone to the home screen and saw that whatsapp was on besides the other apps, my whatsapp is locked with my fingerprint which also can be seen from the apps in memory, so I thought it must be a new UI thing from the whatsapp team, so I tried to emulate it but it did not happen again. Funnily, I never saw that lock icon again after that first incident. Nothing seems out of whack with my phone so I do not think it was malicious, but I am kind of concerned what could that anomaly of a duplicate lock icon be? , a bug perhaps?. I tried searching on google and samsung forums but found next to nothing. I am sorry I have given next to nothing, but this is about the only information I have. Hope somebody can shed a light on this mystery, as I am not going to lie its kind of bugging me since it happened.
Edit : Attaching the screenshot.