Ok, let's say hypothetically it's not the salesperson's job to know everything about the device they're selling. I disagree, but let's assume this, anyway.

Why did the company not send an actual engineer to the trade show as well? I've done plenty of trade shows as a customer and there's almost always an engineer on-hand to assist with more technical questions and issues with the demo device.

Even assuming the prior claim, the company still screwed up not buying another plane ticket for an engineer.