Does skin graft look like a scab?

Anything that looks like a scab should be carefully removed by your surgeon to assess the skin graft take.  Your timing from surgery makes me think you should have a visit soon.  Without an in person visit, it would be hard to interpret the outcome.  Regardless of the amount of take of your skin graft, your wound and size of the scar is likely contracting and will be easy to manage or revise when smaller and fully healed.  Best Wishes!!

After the removal of a skin cancer, a reconstruction is required to close the wound. This might involve a stitches, a skin graft, or flaps. Wound care is important to keep the reconstruction free of infection, so it can heal well. If you have any questions or concerns about the color or appearance of the flap, I would recommend returning to your doctor to be evaluated. Safety comes first.

Your description and post operative status regarding your graft would likely indicate that the graft failed to take.  The way you describe the graft healing is abnormal.  I would recommend you follow up with your surgeon as soon as possible.