I don't touch anyone's lines unless they are at risk of damaging my boat or they are currently damaging theirs.
Those are the only logical reasons to touch anyone's lines. As per the OP, if someone has stepped aboard and ADDED two lines, with nothing being REMOVED from the boat, nothing being disturbed, nothing missing, then, logically, they were there with the intent of solving an evident problem, not causing harm- it was apparent to someone that your boat needed two more lines. Someone will likely own up in the next couple of days, in which case , say "Thanks." they may have saved your bacon.
No one here has a problem with a boat in peril being boarded, and lines being adjusted or added, or halyards tightened or tied off if required. It's neighbourly boatkeeping, that keeps us low on the marina's radar. the more we tend to ourselves, the less we have to worry about the redshirts sending nasty letters about additional dinghies and kayaks or unapproved dock improvements like beer pong tables and umbrellas.
Sometimes after storms the booze fairy stops by our boat, and anonymously leaves beer or wine in the cockpit. Apparently adjusting lines pays off from time to time.