I have a similar problem that is not fixed by the 'Insert' idea that was mentioned.There are no xrefs in my drawing.
I created a detail by copying someone else's detail block into a new document. I exploded the block and recreated the linework. I don't see any extra objects when I'm in my file, but they show up when I 'insert' the detail into my detail sheet.
This may be related also. I have layers in my document from the original block drawing that I cannot delete - I get an error message that there is linework on those layers so they cannot be deleted. But I have done my best to delete all the old linework. Where is it hiding???
Try going to the Layer Properties and clicking on the 3rd icon at the top left. This brings up the Layer States Manager.
Down the bottom section, under Restore Options, there is a check box titled 'Turn off Layers not found in Layer State'
If this is checked, uncheck it and try importing your layer state again.
I looked at the Layer States Manager (which I have never used before) and learned I have no layer states. So, if nothing else, thanks for introducing me to the topic!
Any other ideas for the hidden objects?
Explain how did you import those layers?
did you copy+paste some objects on some layers?
if this is the case? then maybe these objects were insert as a block
and some how (by mistake) were erased.
just copy+paste them again (from the USB pen drive) and thats it.