It may or may not be a graft. Even if it is a graft, one graft would not make a difference in your overall result. If you are concerned it is best to contact your doctor.
At 3 days, if you picked out this graft, or if there was bleeding associated with it, it is probably a lost graft
This is a dried and death hair graft. Some of the grafts may not be inserted in to skin properly and this poor implant technique may cause drying and death of graft.
Most hair transplant surgeons would agree that the stem cells required for a hair transplant graft to 'take' have migrated into the recipient skin by a week so if the hair shaft and scab come off after this, it will not affect the new hair growing in 2-4 months time. If the graft you are referring to came out 3 days post op, a new hair might not grow. But don't worry, In the scheme of things, given the number of grafts transplanted, this will not make any difference to your overall result.