"Reuben returned to the pit, and was surprised to see that Joseph was not there." The word "behold" here shows that Reuben was surprised to find out Joseph was gone.
This is an act of deep distress and grief. This can be written more clearly. AT: "He was so grieved that he tore his clothes" (See: [[rc://en/ta/man/translate/figs-explicit]])
Reuben uses questions for emphasis the problem that Joseph was missing. These can be written as statements. AT: "The boy is gone! I cannot go back home now!" (See: [[rc://en/ta/man/translate/figs-rquestion]])