Write from facts rather than momentum
Pause long enough to remove accusations, assumptions, and details that belong to someone else. For a message about how to follow up on missing project assets, use this factual base: summarize the deliverable, version, requested input, owner, and effect on the schedule.
Offer a proportionate next step
Match the size of the request to the relationship and to what the recipient can reasonably decide now. Give a small set of options and explain which default plan applies if the real deadline passes. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Protect privacy on both sides
Do not bury a scope or price change, threaten the relationship, or pretend silence means approval. Use the contract and documented escalation route for legal, payment, privacy, or security decisions. Use the most private legitimate channel available and do not share the exchange to recruit support or pressure.