can't see the blocks inserted

Give more details.

sorry,... i made a 3d door into a block. it's been inserted into the drawing into the doors layer.
if the doors layer is not visible when i save the file, the next time i open the file and turn on the doors layer, the doors that were inserted are no longer there (visible).
the blocks are still there. i can still insert them. i know if i insert one block, then somehow they all appear again (if i leave the layer visible when saving).
is there any way to save the file without having to make sure the layer is visible each time?
thanks.

You seem to me to be confusing visibility with existence. Either the blocks exist ("are still there") or they don't, regardless of whether they are visible. Please clarify.

check to see if they were inserted at 0,0