I ran into a related issue just today when using displacement for some condensation. To add to what was already mentioned (i think this is directly related) the scale of the UVs seems to matter--aka, if your UVs on a displaced object are not scaled large enough you start getting artifacts where sections of the geo are disappearing. There are other scale related issues like this i've come across as well when changing scene scale, displacement scale etc.
Intel i7-3930K, 64gb RAM, Asus X79 Deluxe mobo, 2x EVGA 780 6gb (for rendering), 1x PNY quaddro k4000 (for display)
Windows 8.1 x64, Maya 2014, Octane Render v2