One is 33 times more likely to fall through the cracks than to slip between the cracks, according to a google search. Remember, Betsy, that I was raised by prescriptivists who taught me that there is good English and the rest, which is below abysmal.
Had I said slip between the cracks they would have corrected ne quite firmly, with ruler cracks across the knuckles. Well, not really, but there were a couple of nuns at the Catholic grammar school who might well have. I'll never forget Sister Agony of the Sisters of Perpetual Menses.
Edit:
And I have, of course, made an imperfect fool of myself by googling "fall through the cracks" when I had actually used "slip through the cracks." But the latter still gets 67KG, even though in thinking about it I would have been more likely to use fall and just slipped in this case.
