I've had the problem in 1.8 where a map in an itemframe would disappear, but logging out and back in again would cause it to appear again and braking the block that it was placed on would cause it the block to drop, followed a a second or so that by the map and item frame.
However, I've just opened this 1.8 world in 15w32b and all the maps on itemframes in my map room have disappeared. They don't seem to reappear when I break the blocks. See the two images
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kumasasa
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When I opened this world in 15w32b I was elsewhere and ran around a Nether Fortress for a while looking for Wither Skeletons... I then headed back to my main base as I was running short of arrows. I saw my map room, so I opened a backup with 1.8, and travelled straight to my main base so has to compare. I've just opened a copy of this world in 15w32b, and the maps are now there.
However, the duplicate UUID bug sounds a possible reason.
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Ran the same world this morning with the launcher open and the log is attached.