Another way water can enter your foundation is through form pins (or form ties). Although this is rare, it does happen. What is a form pin? Well, when they pour your foundation wall the forms used are held together with either metal rods or wooden rods, known as form pins. Older construction used wooden pins to hold the forms together and over time these wooden form pins would rot (as shown in the picture).
More recently, construction companies began using metal rods as form pins and that reduced the possibility of leakage, but it could still occur.
In either case, you will see signs of leakage by the staining on the wall. Both the metal and wooden form pins will leave a mark running down towards the floor.