That's an old Customer Service / Retail adage too. You never tell your customer "I don't know" or risk losing their business. You always make an effort to discover the answer or find the customer someone who has the answer.

Apparently it's so rarely done in IT around my parts, though, that it really impresses the bosses when you "go that extra mile". You could earn mucho brownie points by using that response, Loner. As long as you follow up, of course.