Meh, nothing to worry about.
If this could be done on someone else’s iPhone without their knowledge, that that would be a massive security hole. As is it poses no threat to anyone and is more of a curiosity people can play around with.
The “unpatchable” part is misleading. Apple can’t patch a device that’s had this performed, but they sure can make changes to iOS to prevent this from working in the future.
Apple can’t patch this through an update. It’s a hardware level exploit