Does a land enchanted with an Aura get returned to hand if the Aura is bounced?

When a spell or ability 'bounces' a permanent (returns it to its owner's hand), it affects only the object specifically targeted or specified by that effect. An Aura enchanting a land is a separate permanent from the land itself, so only the Aura moves (CR 400.1: each object on the battlefield is an independent permanent).

The Aura simply ceases to be attached to the land when it leaves the battlefield. The land is unaffected and remains where it is. There is no rule that causes an enchanted permanent to follow its Aura anywhere (CR 303.4c: if an Aura is removed from the battlefield, the enchanted permanent is simply no longer enchanted).

This is different from Equipment, but the rule is similar: bouncing a Sword off a creature doesn't bounce the creature either. The two permanents are always independent objects that happen to have a relationship.

Concrete example: Your Forest is enchanted with Utopia Sprawl. Your opponent casts Unsummon targeting the Utopia Sprawl. The Utopia Sprawl returns to its owner's hand, but your Forest stays on the battlefield untouched and untapped — it just no longer produces bonus mana.

If your opponent instead wanted to return the land to hand, they would need a bounce effect that specifically targets the land (e.g., Unsummon targeting the Forest), or a mass-bounce effect that includes lands among its targets or affected objects.