Secretary Lew was visiting a Palo Alto innovation lab during the outage.
Lew had the economy on his mind when he gave a speech at the Commonwealth Club.
"Too many people are still struggling to reenter the workforce," he said. "You see, our long-term prosperity depends on an expanding and vibrant middle class."
But many investors in the audience wanted to know why the Nasdaq suffered such a colossal failure Thursday, when trading froze for about three hours.
"It's interesting," investor John Thomas said. "I was in the market when that happened, and you could just see all the volume shifting towards other online exchanges that were still functioning."
"I think there's been other glitches, not just today, and that has me worried somewhat," Palo Alto resident Marcia Weil said. "You know, what is that about and what can we do about it?"
Sec. Lew said the securities exchange is investigating, but couldn't say why the glitch happened in such an advanced economy.
"Sometimes there are just system failures where machines break and they need to be fixed and get up and running and you need redundancies, but I am glad to say the markets are up and running," he said.
Ironically, reliable technology was the reason the secretary visited Palo Alto earlier in the day. He toured the AT&T Foundry, a think tank for innovation where different tech companies are investing to develop products and create jobs.
"You saw the app economy, think of how large the app economy is," said Anbi Ingle with AT&T Foundry. "No imagine that app economy going deeper into a network economy we can pull through network services."
Lew was touting the president's plan to create jobs and help industries spur innovation across the country.
The secretary also toured Facebook during his brief visit to the Silicon Valley. Besides investigating the Nasdaq failure, he'll head back to Washington with some innovative ideas born right here in the Silicon Valley.