Dear Client,
Sale could have possible if ur father were at least in a position to sign some document than through Power of Attorney, it was possible.
Here is one way out, If your father is mentally or physically disabled or otherwise incapacitated, and unable to handle his affairs, you may apply to become his legal guardian, preferably Wife.
Apply to High Court to appoint wife/son as Legal Guardian for purpose of dealing with his immovable properties and bank accounts on his behalf to meet out the expanses of his treatment.
Read below Judgement of High Courts, dealing with same situation.
http://www.livelaw.in/bombay-hc-grants-wife-guardianship-husband-comatose-condition-read-order/
https://www.indiatoday.in/pti-feed/story/hc-allows-wife-to-deal-with-assets-of-husband-in-coma-to-meet-[deleted]