If one is going to experience shock loss, it will occur only in the first several weeks post op. Therefore any loss or thinning at the 2.5 months mark is entirely unrelated to shock loss. In your particular situation, shock loss it not probable. After performing hundreds of FIT cases, we are only aware of 2 instances of shock loss in the donor area. Considering the number of grafts you received and the time interval at which the sparseness became apparent, I do not believe you are experiencing shock. In addition, miniaturization in this part of the scalp is inconsistent with male pattern baldness.
It may be that the hairs in your donor lay less optimally due to the strip. Or you may have experienced some minute shedding after the procedure that you are only noticing now (although I doubt this is the case). More than likely you are simply scrutinizing that area more so now.
The result of a HT will progress over the course of a year so it is premature to stress. The area will fill in as the grafts grow. You need to give it time.
Notice: I am not a doctor. My opinions are not necessarily those of Dr Cole. My advice is not medical advice.