“No clue yet, give me an hour to check” earns more trust than a smooth bluff ever will.

A confident wrong answer costs more than an admission of ignorance, because it has to be discovered later by someone who then reconsiders everything else you said. Admitting you do not know yet is a small immediate cost that buys a lasting reputation for accuracy. People can work with uncertainty; they cannot work with information they have to verify.

Practice the sentence before you need it, so it is available under pressure. Pair it with a time: when you will know, and how you will find out. Then come back within that window even if the answer is still unclear.