Writing about memory and the past often brings pressure to produce a complete story. Yet an unanswered question can be an important part of an honest account. Leaving it visible tells the reader where the evidence stops.
Describe the gap precisely. An unknown date, an unidentified photograph and a missing explanation are different kinds of uncertainty. Naming the problem makes it easier to decide what additional material might help.
Explain the work already done without turning effort into proof. Searching several sources may narrow a question, but it does not make an unsupported conclusion more secure. A research note can record a promising lead while retaining its provisional status.
When the piece is revised, keep track of what changed and which source made the difference. This gives the enquiry a readable history of its own. A responsible account can be engaging because its reasoning is visible, even when its final question remains open.