Minecraft Bug

I was playing minecraft earlier today and I was putting some maps into item frames to make them look nice, I had 4 maps and equal amount of item frames, I had them placed in a 2x square, then the bug appeared: the top left item frame disappeared, I was confused (as you would be) and took away the other frames, I scrolled my mouse wheel to change to the item frames to put them back, when I scrolled past the maps, I caught a glimpse of the map showing my direct area and I saw a green marker where the item frame was placed. could someone tell me what happened and see if they could try and do the same, I will find a picture to show everyone and see if this will get fixed.