Indeed Garfield didn't "say" anything, but he laughs aloud in panel 2, which is always unsettling. Jon's barely-stifled anger and willful denial that he was stood up are clear in his clenched claw-hand. So though it might be weird that a man is yelling at his cat in frustration over his rejection, at least here it's justified: the cat is laughing at him.
Part of me wishes Jon had been so delusional as to go ahead and continue his date with an invisible woman, conversing with her over dinner and insisting on buying a meal for someone who isn't there. Another part of me likes that Jon feels the need to make excuses to his pets for being home on a Saturday night. Jon could, of course, point out that Garfield is also alone, and hasn't seen Arlene in more than a year.
Did I seriously check every Garfield strip for the past year to see if Arlene appeared? Of course I did. For you.