Frustration's Cure: A Reference Librarian

This scenario has played and replayed at both libraries where I work:

A student came up to me, frustrated that his database search wasn't working out well.

"I need to find some information about some companies for my business class," he told me.
"What sort of information?"
"Well, like how much money they make and stuff."
"Where have you looked so far?"
"Ebsco, you know, Academic Search Premier.  And we've found a lot of articles, just not what we need."
"Okay, I have another suggestion for you."
Big sigh on his part.  I could almost read "What now?" flashed above his head.

"Okay, what?" he asked.
"Let's try LexisNexis."
I walk him through how to get to LexisNexis using the CRC computers, and then how to access the Thomas Register and Standard & Poor's reports for Pepsi and Coca-Cola, his two target companies.
"Wow!  That's really cool!" he says, looking at the wealth of information.  "That's everything I need for class!"
"I'm glad it will help."
He's still marveling at how easy and fast looking up the information is.
He looks up at his friend who is still scanning a monitor, his finger rolling over and over the scroll button on the mouse.
"You know what else?" the student asks me.  "I can also use this to choose my companies for my portfolio for the final!"
I nod.  His friend's finger is still rolling over and over.
"Thanks!  You've really helped," the student says, slinging his backpack over his shoulder and walking out of the library.
His friend?  Still scrolling away.

It's at times like this my biggest dilemma sets in:  Should I go over to the friend and say, "I think I know what you're looking for, and I can help"?  Or has he gone on to a new quest and doesn't need my help?

Try not to be too invasive is the library school motto.  So I sit at the reference desk, occasionally glancing at the student.

Is his frustration level rising?  Does he know to ask me for help?

I wish I knew the answers.