Just check the scale of the detail that is inserted into the sheet. When you insert the detail into a sheet that is 1/4"=1'-0" and went back to the detail and changed the scale to 3"=1'-0", you wont be able to see it on the sheet because it got bigger than your sheet and its off, but it's still there. You just have to bring it back to 1/4"=1'-0" scale.
hope this helps