When you place an item frame, and slowly move your cusor into the sky, the item frames disappear. This is not a F1 only bug, I just enabled F1 so it'd be more clear to see.
MC-19224
Item Frames Disappear when looking into sky
Resolved
Duplicate
0
Tom Scheeper
(Unassigned)
Unconfirmed
Minecraft 1.6
Retrieved
This could be a duplicate. But after 5 minutes of searching whether this would be a duplicate I stopped searching. Took me too long.