It comes down to motive and reverence. God certainly doesn't need a buried statue to help you sell your house, but the fact that you made an act of faith by doing something as odd as burying a statue of St. Joseph is what matters.
Respectfully, I am interested to read your more about your perspective that burying a statue of Joseph and act of faith?
In Christ...
Any kind of prayer is an act of faith. This is not sublime theology, but even the simplest trust that a saint can assist us with their intercession is a trust that God values the prayers of the saints, as demonstrated in Revelation. It just depends on what the motive for doing it is.
e.g., a Christian can wear a gold cross on a chain as either a) a sign of Christian devotion, or b) a fashion statement. One is pleasing to God, one is not. In the same way, one can bury a statue of St. Joseph as a) a kind of demonstrative prayer of belief in God's power to intervene in human affairs, or b) a belief that by burying a statue, God will make you fabulously (or modestly) wealthy/successful on demand.
In Christ...