Disappearing imagery at various scales? This sounds reminiscent of something I encountered a while back.
First though, I would make sure that the mosaic dataset is visible at all scales. Right click the layer in the table of contents, pick "properties" from the bottom of the list, pick the "general" tab, and make sure the radio button for "display at all scales" is selected.
If that's right, here's what I had to do, with an earlier version of ArcMAP (10.0). From an email, I wrote to a colleague at the time:
[INDENT]I was able to figure out how to get rasters to show up, when they seem to go away at small scales. It appears to be a pyramid problem.
Two steps: You have to (1) delete the existing pyramids, and then (2) rebuild them. At least, this worked for me.
To do this, you'll need a tool in the toolbox: under �??Data Management | Raster | Raster Properties�?�, you�??ll find �??Build Pyramids�?�.
Step (1) Delete existing pyramids: Execute this tool, enter the problem raster data set, and then click �??Environments�?�. Choose �??Raster Storage�?�, make sure �??Build pyramids�?� is checked, and, in the Pyramid Levels, enter �??0�?� (zero).
Click okay, and okay, again, to execute the tool.
Step (2) Rebuild the pyramids. After step one is done, run the same tool again, with the same raster, but this time, make sure the �??Build pyramids�?� check box is checked, but leave the pyramid levels blank.
Click okay, and okay, again, to execute the tool.
I know, it�??s weird. First time, with �??0�?� levels means �??delete pyramids�?�; the second time, with �??blank�?� for levels, means, �??rebuild them�?�. [/INDENT]
Maybe this will work for you. Good luck.
Cheers,
-Bruce