In scouting my opponents, I found the Protoss Cybernetics Core warping in (during its final warp in animation stage), but as soon as I left vision, the core dissapeared from the FoW. To be clear, I scouted it during the 'completion animation phase' and left vision before the building had finished warping in. It was however still visible on the minimap, just not in the main screen (though if I put my mouse over that area, the opponents name would pop up indicating something was there).
I accidentally deleted the rep somehow (fml), so I attempted to reproduce the effect in a custom, and it was actually easy to do so. I could not figure out if this is the case with all Protoss buildings during that final phase, but I tried to find out if it was the case with the pylon, which I couldn't reproduce, and the gateway, from which I could reproduce.
Below are two short replays showing the Cybernetics core and Gateway disappear in the FoW while in this animation state.
[Cybernetics Core]
http://drop.sc/40273
[Gateway]
http://drop.sc/40915