Read the comic here.
Yeah, I'm a day behind. Things will get caught up sometime this week.
Fox's signature on the note is supposed to have a cute little "couples only" thing in it. Signing a note "XXOO" is shorthand for "hugs and kisses". So Fox has adapted that into something uniquely her own.
Not sure if it really came across in the strip, but that's what I was thinking, anyway.