SPOILER: Trunks

They dialogue says it only proved a 90% likely match that it was her husband. Not definitive. Also, the trunks they showed her from the body were light blue. If you scroll back in the film, when he disappears they're black or very dark blue trunks that he's wearing, not light blue.

She was probably telling the truth when she said it wasn't her husband's watch and not her husband's body.

Perhaps the film ends as it does because she genuinely can't find resolution and closure, so our experience at the end of the film mirrors hers.