The guard was greatly disturbed, because there were millions of dollars of computer equipment inside, so he watched the man carefully.
When the man was leaving, the guard took him aside, searched his clothes, and nothing was found.
The next day of the trade show, the man returned and the guard watched him even more closely. When the man was leaving, the guard took him aside, searched his clothes, nothing was found.
On the final day of the trade show, the guard couldn't restrain his curiosity any longer, he asked the man, "Did you try to fool me or what? What were you actually stealing?"
The man replied, "I was stealing ideas."