If you actually met some of the guys that tear down the bikes at the plant, you would probably rather have them send the bike in pieces to a dealer and have the TRAINED TECHNICIAN put the bike together. Had it been caught on the line, the bike would've been torn down and basically a different bike would be built with the same components, no different than the technician doing it at the dealership really. I do feel your concern about the split frame but as you said, mistakes happen. I've seen missed welds on more than one occasion that were caught in the factory so it's only in due time that some get out. The bad thing is, they need to go back to the date the bike was offlined (not the build date) and see if any other bikes have the same missed weld, but that's not possible since the bikes are already out the door.
Post your build date and build # if you have it. Maybe some of the other guys within 50 bikes +/- of yours are on here too and they can check their frames.