How can the Investigating agency escape liabilities, when a key witness is said missing in a serious offence ?

As per a recent news report, released yesterday in Times of India, the Chandkheda police official said: "We have learnt that Shrenik Shah, a key witness of most debated "Sanjiv Bhatt" case involving some serious allegations against Mr. Narendra Modi, CM of Gujarat, has been missing from his home. We have spoken to his family but they are not yet ready to file any complaint. We can do little at this juncture." it is also said that a Police Constable Pant has filed a complaint against Sanjit Bhatt with the Ghatlodia police which is investigating this case, and this Shrenik Shah had become a witness and his statement was recorded under 164 CrPC. A statement made under this section, before a judicial magistrate, is difficult to go back on. Any person who chooses to make a volte face after this is liable for imprisonment too. But the crucial questions of facts and laws are now raised at this stage, how the investigating agency can escape their statutory liabilities under the laws to investigate such a serious matter to meet with the ends of justice, just by saying that it can do a little in such case... Is there any legal effective solutions to prevent any such other overriding factors, which are prevailing upon an independent investigating agency ?