You can do a lot of fixes with hose clamps, u-bolts, etc. And they are perfectly fine. The only thing you need to be careful about is that you don't have an actual hole in the exhaust system under the car. It probably isn't so much a problem these days with better build quality, but you don't want carbon monoxide seeping into the passenger compartment from a hole in the exhaust system underneath.
Fortunately, holes are usually easy to detect. You hear them!
Mufflers really do a great job, and any exhaust leaking out before the muffler makes itself conspicuously known. And once you have narrowed down the general location from the sound, you can run your hand along the system (being careful not to actually touch it and burn yourself) until you feel it - it will be puffing out with a pretty good force.
VEFF wrote:I don't think the owner even realized it
I'm sure he noticed it (unless he was deaf). He probably just didn't care or didn't know what to do about so just drove on.