Absence is evidence. No fly adult in the trap for a week and no larva in twenty cut stems weakens a pest explanation for dead pinheads. Inlet end and far end looking identical weakens an air explanation. Trouble in bags from three compost batches rules out one bad batch.
Negative evidence has one rule: it counts only if you actually looked, in the right place, with the right tool. "I saw no mites" means nothing without a hand lens. "Temperature was fine" means nothing if the thermometer hangs by the door instead of sitting in the bed. Record what was checked, how and where.