Final answer:
Without additional information, it is not possible to determine the missing dimension of the rectangular face of the pyramid given only one dimension (3 feet).
Step-by-step explanation:
To find the missing dimension of the rectangular face of a pyramid when one dimension is given (3 feet), you generally need additional information about the pyramid such as the ratio of the dimensions, the area of the face, or an association with another geometric figure that reveals the missing dimension's value. Without this information, the second dimension remains undefined. As no such information is provided in the question or the provided context about various historical pyramids and their dimensions, it is not possible to accurately determine the 'blank' feet dimension of the pyramid's rectangular face.