Is this your local or central file?
The ID you get from that message, write it down, search for element by I'd, delete it. But, you need to try detaching from central with audit checked first (cross your fingers you can open the model). I've known a few manuf families that caused some nasty errors before but I've been lucky enough to always get a model open (I've lost several man hours of work--a few days worth at worst--but I've been somewhat fortunate). Good luck.