The Wicker Man

Sergeant Howie (Edward Woodward) journeys to the remote Hebridean island, Summerisle, to investigate the disappearance of a young girl, Rowan Morrison (Gerry Cowper), about whom he has received an anonymous letter. Howie, a devout Christian, is disturbed to find the islanders paying homage to the pagan Celtic gods of their ancestors. They copulate openly in the fields, include children as part of the May Day celebrations, teach children of the phallic association of the maypole, and place toads in their mouths to cure sore throats. The Islanders, including Rowan's mother (Irene Sunters), appear to be attempting to thwart his investigation by claiming that Rowan never existed.
While staying at the Green Man Inn, Howie notices a series of photographs celebrating the annual harvest, each featuring a young girl as the May Queen. The photograph of the most recent celebration is suspiciously missing; the landlord tells him it was broken. The landlord's beautiful daughter, Willow (Britt Eklund), attempts to seduce Howie, but he refuses to have premarital sex.
After seeing Rowan's burial plot, Howie meets the island's leader, Lord Summerisle (Christopher Lee), grandson of a Victorian agronomist, to obtain permission for an exhumation. Lord Summerisle explains that his grandfather developed strains of fruit trees that would prosper in Scotland's climate, and encouraged the belief that old gods would use the new strains to bring prosperity to the island. Over the next several generations, the island's inhabitants fully embraced the pagan religion.
Howie finds the missing harvest photograph, showing Rowan standing amidst empty boxes. His research reveals that when there is a poor harvest, the islanders make a human sacrifice to ensure that the next will be bountiful. He comes to the conclusion that Rowan is alive and has been chosen for sacrifice. During the May Day celebration, Howie knocks out and ties up the innkeeper so he can steal his costume and mask (that of Punch, the fool) and infiltrate the parade. When it seems the villagers are about to sacrifice Rowan, he cuts her free and flees with her into a cave. On exiting it, they are intercepted by the islanders, to whom Rowan happily returns.
Lord Summerisle tells Howie that Rowan is not the intended sacrifice â Howie himself is. He fits their gods' four requirements: he came of his own free will, with "the power of a king" (by representing the Law), is a virgin, and is a fool. Defiant, Howie loudly warns Lord Summerisle and the islanders that the fruit-tree strains are failing permanently and that the villagers will turn on him (Lord Summerisle) and sacrifice him next summer when the next harvest fails as well; Summerisle angrily insists that the sacrifice of the "willing, king-like, virgin fool" will be accepted and that the next harvest will not fail. The villagers force Howie inside a giant wicker man statue, set it ablaze and surround it, singing the Middle English folk song "Sumer Is Icumen In". Inside the wicker man, a terrified Howie recites Psalm 23, and prays to Christ. He curses the islanders as he burns to death. The wicker man collapses in flames, revealing the setting sun.

Question: What does Howie find ?
Answer: Howie finds the missing harvest photograph.