Over the millennia the leaf ceased to be and the sediment formed the fossil.
No, it didn't. Ground water containing dissolved minerals might have formed the fossil, if it was a replacement sort of fossilization event. Or surrounding sediments might have made a mold that preserved the shape of the leaf. But the anthill grains themselves didn't "form the fossil."
And in answer to your topic title: no, Buz, I won't go out with you. I'm a happily married man.
One answer was that the glue including mineral and whatever factored in, but that doesn't make sense to me, in that the aged glue itself would not necessarily record when the organism was deposited.
True, in the strictest sense. But if that leaf hasn't had its original tissues replaced by minerals in, say, 50,000 years or so, there won't be a fossil left for us to see (unless it is perhaps a cast) after a few million years. A 50,000-year error in a date of 50,000,000 years is the same size of error as being an hour off in something that you remember from 41 days ago - early February. Not a deal-killer in the question, "when did this leaf fall." Patticularly when the leaf is of a sort that has never been found on a modern tree.
If the flood happened, the dating data recorded would be off due to unknown pre-flood consistency of the atmosphere elements and that in organisms.
So did the pre-Fludde atmosphere have uranium, rubidium-87, and potassium-40 floating around in it? Carbon-14 dating relies on stuff in the atmosphere, yes, but the things that get used to date dinosaurs don't. And the contents of organisms don't have doo-squat to do with the ages of, say, Devonian rocks. It isn't the fossil itself that gets dated, Buz.