Yes, those detox potions are a big scam. Their makers tend to make any claim in the world in order to woo in the credulous and taking their cash.

However, its not uncommon for longtime heavy smokers to take up to 60-90 days to finally test negative. Actually, the longest ever reported was 105 days. This person was a heavy user for many, many years, weighed in on the wrong side of 375 pounds, and indulged in zero physical activity.

I think if people have failed tests of any kind after even 30 days they have been smoking or are around others who are.
People failing urine tests because they have smoked. You cannot test positive on the basis of secondhand smoke.