Can a cold sore be recreated by cellular memory, even after the causal virus has been removed from the body?

This is quite correct. As with other illnesses of karmic origin, a resonance with what is in the akashic records can bring around a re-exposure to the energies of any part of the problem not yet fixed thoroughly. Healing is an incremental process. What that means is that even when symptoms fade and are no longer on the person's mind there can be residual traces of its origins, and a conscious focus on prior events as well, can stir up trouble and re-create even a full-blown illness. In addition, the remnants within cellular memory might not be fully healed even after a long span of time being symptom-free. So an inner rumbling from reminders of the past can indeed trigger cellular memory to mount a re-creation of symptoms from old maladies and this applies to even simple things like cold sores, as well as severe chronic organ compromise.