David, welcome to a group that you probably never expected to join!
It is very possible that there might be an unusual amount of scar tissue and your urologist is doing the right thing to go back and do a biopsy to be absolutely sure. In fact, a second TURB (biopsy) is considered good medical practice if there is any doubt. It is also common to have urine cytology done to look for abnormal cells, although this sometimes gives a false positive result.
BCG is usually not recommended for a first occurrence of bladder cancer that isn't high grade, as it is not as effective and they sort of save it for when it might really be necessary.
I
The usual protocol for low grade bladder cancer is to have cystoscopy (looking inside the bladder) every three months for two years, then every six months until five years have passed and then once a year forever. The problem with bladder cancer is that it has a nasty little trick of coming back and they want to find it fast if it does.
Hope this answers some of your questions.
Sara Anne