I clean a church once a month (spots) and clean the entire carpet every 6 months.There is a spot that totally dissappears when we clean it as soon as carpet dries its back. This has been happening for the past year. The pastor and secretary has also seen this .What could it be or do you dare have the answer.The pastor thinks its funny!!
Could it be oil of some sort? If it is, it will act just as you are describing. If you think its oil, you could use dry solvent, or tgp on smaller areas. If it’s a large spot, try our portable extract. Directions for this are in your manual. Good luck.