First, I think this is related to my post here:
<a href="http://community.roll20.net/discussion/3346/cant-delete-oversized-item-#Item_12" rel="nofollow">http://community.roll20.net/discussion/3346/cant-delete-oversized-item-#Item_12</a>
I think the preset for the grid/layers in the top left corner are jaunting images outside of the grid where they are unobtainable...more specifically larger/oversized images.
I put a large photo in by mistake the other night, and the image is saved in the memory, making it the icon for the map on the tabs, but its nowhere to be found.
I think the dead space around the visual area needs its limitations refined so objects outside of view are pushed back into the grid/visible area each time the map gets loaded. It may be more beneficial to DMs if this only happened if the center point of a token is outside the visible area...