An entity with no relationships will evaporate, so editor is warned by message: 

“This [entity] has no relationships and will be removed automatically in the next few days. If this is not intended, please add more data to this [entity].”

As a “few days” is a bit vague, and editor's window may hinge onto other than own room (e.g. an add-area ticket coming through), I suggest the warning specify a deadline, and at the same time bettering the current “more data” (an artist in solitude will not be saved by, say, having birth date added): 

“Entities without relationships are removed automatically after n consecutive days’ solitude. This [entity] has no relationships, will therefore be removed automatically by yyyy-mm-dd hh:mm. If this is not intended, please add relevant relationships to this [entity].”