Faking an answer at work costs way more than the five seconds of looking new would have.

A confident guess gets acted on. The five seconds you saved by not admitting uncertainty are repaid by whoever builds on your answer, finds out it was wrong, redoes the work, and then wonders what else you were unsure about. The cost does not stay with you, which is part of why it is easy to pay.

Use the short sentence instead: you are not certain, you will check, you will come back in ten minutes. Then actually come back. Doing that twice in a week quietly establishes that your yes means something.