Share certificate is not a title document.
Bank is not obliged to grant loan on the basis of share certificate.
A share certificate is issued by the society or the apartments association and it is not a registered title document to prove one's ownership to the property.
The marketable title to the property can be established only by a registered sale deed document in possession of the borrower in his name.
The bank cannot recover their debt in the event you default the repayment on the basis of share certificate.
What happened to your sale deed document, how come you are not having title deed document but are having share certificate?