Help the unfortunate camper express his deep regret about last weekend's disaster.

If we had remembered to pack the tent, we ___ to sleep in a cave full of angry bats last night.

The correct answer is wouldn't have had.

This is a Third Conditional sentence, used to express regret or talk about an unreal situation in the past. The structure requires: If + past perfect, would have + past participle. Here, the past participle of "have" (meaning "need to") is "had".