I take it that you are sanding the old finish off? Unless you are really careful, yes, it will disappear. I usually tape the signature area off and sand on both sides to remove finish and then remove the tape and finish sanding by hand around the signature. Then lightly sand the signature to see if it lightens. If it does not then you can sand a little more but be careful and work slowly.
Sometimes cue makers sign between coats of finish as I used to do.