Have you seen this happen before?
Does the muffler have to be replaced as well? Or does it usually kill that as well?
Your Muffler should be fine, unless small chuncks of the cat broke loose and went thru the exuast system. How old is the exhaust system on it? Are you planning to keeping the truck for a while or just short trem? If it was me, I would just replace the entire exhaust system, if I was planning to keep it. Again that's just me....