The fact that the Eternabond came unstuck says that either the roll you had was defective (highly unlikely) or that there were contaminants on the surface that did not get removed by your cleaning regimen. Or the fairies came along over the winter and pried it up. But I won't go for that one.
Acetone is a powerful solvent. But it does not dissolve EVERYTHING. In particular, there are substances that work very well to prevent adhesion that acetone won't touch. Acetone will remove many waxes water won't affect. And water will remove many other problem residues that acetone won't touch. By scraping away the frost and going straight to acetone, you would have left intact a lot of crud that got there in the first place via water.