It was also suppose to be Rand in "What are Little Girls Made Of?" instead of Chapel.
That's the first time I've heard that, although they did toy a bit too much with Chapel's affections, making her pine over Spock few episodes before or after, depending on air date order. If it's true, it's a shame. I rather liked Rand and a lot of development opportunities were lost. I do like guest crew too, I just lament the fun ones that only appear once.