I feel you.. I had the same experience with our eldest. He grew up with my parents from his 8th months to 4years. I also had that experience when I went to visit him on his first birthday. He did not recognize me despite only being separated for about 4 months that time.
One time he woke up in the middle of the night and cried. I could not make him stop. My mom came in from the other room and with just the sound of her voice - "ooooyyy" my son stopped crying. Then I started crying. It hurt so bad not being able to comfort your own child...

Don't feel sad, you are doing what is best for your son. Although hopefully, you get reunited with him sooner. Cheer up!