The Parable of the Prodigal Son is the third in a sequence.
Just before it, Jesus tells of a shepherd who leaves ninety-nine sheep to find one lost one, and a woman who turns her house upside down to find a single lost coin. Both search. Both find. Both celebrate.
Then Jesus tells this parable—and the father doesn't search at all.
Why didn’t the father search for his lost son?
The NIV Quest Study Bible, one of 70+ resources available with Bible Gateway Plus, answers the question directly:
In this parable the younger son had to find his own way home, though diligent searches were made in the two preceding parables. Why the difference? Because analogies go only so far; parallels are seldom complete. The coin and the sheep, for example, were unable to return without help. People, on the other hand, can choose to return or not. Still, the father saw his son while he was far away and ran eagerly to meet him, showing how much he had been longing for his son's return.
The son chose to return. The father had been watching for him.
That's the distinction the parable makes: not that the father seeks, but that he never stops watching. And when you come back, he's already moving toward you.
These questions are worth sitting with before you move on:
Do you relate more to the younger son or the father? What does it mean that the father was watching—not searching, but watching?
Read the full parable: Luke 15:11–32