I've been remiss in telling the latest on this story. Since I was planning on installing a new toilet on my visit next month, Mom passed on having a plumber friend of a friend look at it. After some persuading, she caved and let the nice guy come over to look at the commode. He said he can't see any sign of a crack. Maybe the original plumber didn't do anything at all to stop the leak, all the while planning on coming back and offering to install a new toilet for $309 on top of the $341 for the first service call. That $309 was reduced by half of the $282 for the original repair. Their normal cost for a new toilet is $450 installed.
The plumber, the affordable one, told her to fill the tank back up and call him if she had any more water on the floor. While he was there, he put a new washer in the shut off valve so the water to the whole house didn't have to be turned off to service the toilet. He wouldn't let her give him anything for the washer. The original plumber wouldn't do the shut off valve repair because that would have been an additional service that he would have had to charge her for.
Well, now she's got the name and number for a good plumber that will get plenty of good press in the neighborhood.