ghost blocks

Hello, can someone help or tell me if its possible to find and replace ghost blocks in autocad 2010 LT?
Ghost blocks have appeared from our client, im not sure what software they use
to extract data from their GIS but when we get hold of it, it has blocks which when double clicked to edit do not appear in the list of that drawing's current blocks!
the drawings provided by our client are in dxf format.
my ultimate goal is to find and replace these ghost blocks using express tools (I appreciate LT doesn't have express tools available but we do have a single full license of 2010).
Is there any way of changing these ghost blocks into real blocks that cad recognises?
Sorry for rambling, and thanks to anyone who can provide some help or confirm if this process is (or isn't) possible.
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