Kitchen Large Electric Appliances - dryer problem

A friend of mine has a hole somewhere in the ductwork. She had hired a vent cleaning company because the dryer was not working very well. They inserted an air hose into the vent from the outside and gave short blasts of air while they ran the hose down the vent. (The dryer was turned on to blow out as they knocked lint loose.) They kept running the hose down and pretty soon they had 20 foot of hose in the vent. It’s not 20 feet from ground level to the dryer in the basement, so something seemed wrong. They went down into the basement and could hear the air hose halfway across the ceiling. Is there any way to determine where this hole is, or will she just have to start cutting sheetrock away until she finds it? And what kind of business would one call if she wanted to hire someone to find this hole?

Also, she was told to buy a booster fan for the dryer. Is this a good investment, or a waste of money?

A handy man or HVAC company is who you need to call. Wall will have to come out. No fan needed.

Thanks Airman!

Oh, any idea why I'm not getting email notifications when I have a reply? I've noticed that the last two times I've posted. I always ask for an instant email notification and they are not in my spam folder.