Removal of lien on fd

We had obtained a bank guarantee against FD. BG was dated 4/5/2015 & expiry date was 3/5/2016. It is already a long time since BG was expired. BUt still HDFC bank has not removed lien on FD. They ask to return the original BG. We have misplaced the original BG documents. Please suggest us further for removal of lien on FD & can a bank hold the lien even after the expiry of the BG ask to submit the original BG.