Unusual Incident

Hello,

I have a 2012 Prius plug in with 49K miles. Two weeks ago I started hearing a noise like a rattle over bumps and a faint clunk when the car takes off and stops coming from the front of the car behind the windshield, I think from the engine area. I took the car to the dealer and explained the noise above. They had it for the whole day then I was told that they did not hear anything.

To my surprise when I picked up the car at the end of the day, the noise was completely gone. I noticed that they took my towels out of the middle console, so it appears that they went in there. It's good news, but I don't understand what happened.
Is it possible that it was a simple issue and the technician did a minor routine adjustment not realizing that he fixed the problem? Is that possible? Can anyone explain to me what happened please?

Thanks
Mike

 

Actually, the noise is gone completely, but what I found unusual is the dealer is telling me that they couldn't duplicate the noise. The paper work doesn't mention anything and the service adviser says that he drove the car and he didn't hear anything.
They usually do a routing inspection every time the car gets in, so perhaps the technician adjusted something during the inspection not knowing that it has fixed the noise problem. Well I'm thankful that the noise is gone.