Thanks, Pluggy, for the alternate suggestion, but I am so uninitiated in Linux I am afraid I'd screw it up.
I, too, was surprised to learn from mrtaylor that 0022 was out.
mrtaylor, I changed the Find command per your suggestion, and the only two librxtxserial files that it found were in the Arduino 0021 and 0022 packages. I initiated a file search of my own under the Places pulldown, and those were the only two found. Does this mean that when my son built this machine that he may have missed a library file? I think I've successfully used the USB port on this machine in the ast, but am not sure of that.