This a very common problem for carpet cleaning, what you actually see is called a WICK BACK, this phenomenon occurs a few days after cleaning when the stain resurfaces due to poor carpets drying process after wash where the carpet hasn’t dried properly, the stain particles sink at first then reappears after the drying is completed. When dirt and soil are in the carpet pad, fibres act as a wick, absorbing the stain and dirt and then lifting them back to the surface.