Land with deed of sale and tax declaration, no mother title

Hi! My parents bought a piece of land about 20+ years ago. They have put a large amount of money in renovations of the house that came with it, not knowing that we need to have a title to legally own the property.

My mom was already trying to look for the mother title to no avail. There’s no copy of the mother title in our Municipal hall, since it burned down many years ago. The seller also moved to Mindanao after selling the land, and my parents have lost contact with him.

Parents are giving us a portion of the land to build our own home. The thing is I want to fix the title first, since building a house costs a fortune and I don’t want to have problems with it in the future. My mom was sort of saying she reached a dead-end with the mother title after asking around for advice. But I shouldn’t worry since we have the deed of sale and tax declaration.

I hope someone can help out. I deeply appreciate it!