T-Gel Shampoo and Recent Hair Transplant

20 days post operation.

I am a 24 year old male and just had a hair transpant (2000 grafts). Everything seems to be going OK, however, I used a Tar Shampoo (T-Gel) for direct shampooing on the recipient area (twice) before reading that this may interfere with the growth of the grafts. I have switched to another shampoo, however, I am wondering if this has already affected the transplanted area in a negative way.

You can burn the hair below the skin. For a description of the product and its risks read MedicineNet. It would be unusual to negatively impact the new transplants at 20 days. You should go back to the doctor who did your transplants and ask him/her. I generally advise that after a transplant, you use gentle shampoos like baby shampoo, which is safe and will not burn the skin.