That is true but unning a
netstat/ -a command
will show all the current ip's in use.
If the messaging program is the only one active on the ethernet all the ip's in use will be returned.
I'm not writing this to make you nervous again Kensei as I SERIOUSLY doubt "your guy" would have a clue. And as you have cut off communications with him he doesn't stand a chance anyway and,
AGAIN, the end result would be the same.
ONLY the physical location of your ISP would be revealed.
BTW.......tracking down Yahoo IP's is nearly impossible if NOT impossible.......