No, not all urine stains will glow. Also, what happens is the customer may use either a surface spot remover or may try to clean the surface of the carpet leaving the bulk of the urine in the pad. Sometimes the UV is extremely important to locate the urine while other times you have to do some detective work. You really need a good moisture detector along with a UV light or I can guarantee you will miss a lot of it. Urine will travel below in the pad. I've seen some spots on the surface travel as much as a foot or more in the pad in one direction. If they haven't tried to do something to it themselves a lot of time the stains will be easily visible. I advise getting a moisture sensor. I couldn't live without one. https://https://shop.truckmountforums.com/hydrosensor-i-moisture-sensor.html
I also find it helpful to keep one of these with your UV light. https://https://shop.truckmountforums.com/wet-check-hydrosensor-moisture-sensor.html
Urine can literally stay damp for years. I've seen it many times. It can attract moisture to the deposit.I theorize that urine if left in a carpet could set off a moisture sensor after many decades. I also find the moisture sensor can help you distinguish between a urine stain and something that just looks like urine. I've seen numerous times where urine spots that were literally everywhere would not show under UV, but were obviously urine. I'm not undermining the importance of UV, just adding that it takes more than that alone a lot of times.