Ford 1999 explorer xlt v6

I recently had my fuel pump, spark plugs,
and oil changed all to new and once I drove it
the performance was amazing! But! I
randomly started hearing a noise that was
like someone put a marble in a sealed can
right underneath me nearly. Found out it was
my catalytic converter and it did it for about a
week. And now it’s completely stopped. My
car runs absolutely great still. The gas
mileage has gotten better and the response
is so much faster. So my question is... why
doesn’t it make noise anymore? Did the
problem just go through and out the back of
the car? Should I be concerned?