Might it be that a a hernia push on blood vessels or arteries and cause loss of blood flow to lower part of body?

Doubtful. A hernia is a hole in the abdominal wall, and the blood vessels to the abdominal contents come from the back of the abdominal cavity near the spine, so while i suppose anything can happen, i can't imagine a scenario where the hernia is blocking blood supply. Whatever is going through the hole can have its blood supply pinched off, and in its most severe form is called a strangulated hernia.
Never seen it. I have been in medicine for 20 years, and I have never had a patient with what you describe. However, it would be possible to use ultrasound to look at the area, and determine if there were a blocked artery or vein to the leg. The tests would be an arterial ultrasound and a venous doppler.