Who did we lose back then? We lost priests, yes, but I don’t believe any bishops.
Well, there were several German bishops if I recall correctly (The Peace of Augsburg mentioned them but not by name). Here are mentioned two but not by name: http://books.google.com/books?id=fIhb4-iBk6EC&pg=PA56&lpg=PA56&dq=bishop+german+converted+to+Lutheranism&source=bl&ots=3_IoLqE66s&sig=x68V2ffXo3F9AGz4DE9H0PqKfLA&hl=en&ei=hpBDTIGIC4T0tgOjmIzSDA&sa=X&oi=book_result&ct=result&resnum=8&ved=0CDMQ6AEwBw#v=onepage&q=bishop%20german%20converted%20to%20Lutheranism&f=false
Although this says not a single German bishop did convert: http://www.jstor.org/pss/2543066
Huh! This one converted in the 19th century: http://books.google.com/books?id=gFZE8zTto20C&pg=PA333&dq=bishop+german+converted+to+Lutheranism&hl=en&ei=9JFDTPODPJTCsAOCq5DxDA&sa=X&oi=book_result&ct=result&resnum=2&ved=0CDIQ6AEwAQ#v=onepage&q&f=false