It means the memories last, even if contact is lost.
What is the meaning of even if contact is lost here?
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To say that contact is lost means that it is no longer possible to communicate with someone or some group. This might be temporary or permanent.
This can happen for all kinds of reasons. On a personal level a friend might move to a new address or get a different phone number, meaning that you lose touch.
On a technical level, radio or other forms of electronic contact may be lost with ships, aircraft or spacecraft.
In your example the writer is saying that you retain the memories of someone you have known even when you lose touch with them.