I am a bit confused by the middle of your question but someone else might figure out what you are asking.
However some people are smart enough to drop shields, attack and reshield very quickly so you might not notice.
Is the jarl you are talking about always in the same place?
You can teleport, attack and teleport away again, so you probably wouldnt see tracks as its over so quickly.
If someone attacks from a distance you should see tracks.
If players increase the watch tower, you get alerts on attacks on towns, but not on tiles.
I am guessing that you are in a new kingdom, when everything can be quite frantic,and your mystery player could have moved from another kingdom and is much further advanced in the game.
Check stats and town and hero levels.This should clue you in on expertise and progress in comparison to yourself and others.