How can I the obtain original parent deed of our part property.

Hello I have applied for education loan for studying abroad in a nationalised bank a d offered our house aa collateral. Everything is accurate we gave our original property papers to bank but they also need the parent deed original copy as its our part property, we only have the photo copy of parent deed. The original might be with the builder with wjom we purchased our plot but we dont any of his contacts. Can you suggest any way now or how can we get our original parent deed or any other way. My loan process is not going ahead only due this issue which every bank demands. Please suggest help. Thank you