1. The gift deed can be revoked, if there is no objection from both the parties.
2. You can get certified copies of the gift deed. A newspaper advertisement can be given stating that the original property documents pertaining to the property in question have been lost and asking the public to refrain from doing any transaction with respect to the said property, from any person other than you.
3. There is no need to revoke the gift deed as a lot of stamp duty must have been levied in order to execute such a document. Father-in-law even if is in possession of original documents cannot transfer the property in another person's name. You should rather cancel the POA given to him. A police complaint can be given against him too.