The original smart pigs were looking for what the pipeline industry knew the problem was. You can read the NTSB sumary
http://www.ntsb.gov/publictn/2001/PAB0103.pdfAnd note a smart pig was ran in 1997.
As in airplane accidents a lot of information is gained from crashes, since this failure the smart pigs have gotten a lot better capable of gathering more information. The anomalies that were found at this incident are now looked at when the logs are reviewed.
But when you read the thread starting article the issue was this failure was due to a welder issue. And that is simply not correct. This was a manufacturing issue that was discovered over 30 years after manufacturing and installation. And the girth welds which were welded SMAW are still in good condition with no issues.