After Sam first turns invisible everything he is wearing and anything near him turns invisible. The bandages they wrap him in to bring him to Intersec should therefore also be invisible - as well as the chest plate and anything else he is wearing.
While monitoring Sam's invisibility with her watch, Abby tells Leonard, "He's visible again -- total elapsed time 7 minutes and 11 seconds" which is what it says on her watch. But her watch shows the time that Sam can remain invisible, not the time elapsed.