"Long-lost memories" is a way to describe memories that have not been thought of or remembered for a long time. This phrase can be used to refer to memories from one's childhood or any other time in the past that has not been revisited in a while.

Here are a few examples of how this phrase can be used in a sentence:

"As I was looking through old photo albums, I came across a picture that brought back long-lost memories of my childhood." (当我在翻旧相册时，我发现了一张照片，它带回了我童年时期那些久违的回忆。)

"I was pstening to an old song on the radio and it reminded me of long-lost memories from college." (我在收音机上听着一首旧歌，它提醒了我大学时期那些久违的回忆。)

"After visiting my hometown, I was flooded with long-lost memories of growing up there." (回到家乡后，我充斥着在那里成长时那些久违的回忆。)