What reason could make this situtaion?

I create a couchbase cluster in my PC which is allocated 4GB memory. And I created and saved many data in it.
one day,My companion wanna to jion my cluster by another server machine which memory is only 2GB. Finally he faield and he was told his machine’s configuration is too low to jion my cluster ,which is reasonable.
But the data in my cluster are lost!

I was wondering why could be this and is there any approach to prevent this?
Any help will be appreciated!