Their intelligence told them that adhesive notes would provide the perfect disguise for their drones: innocuous and ubiquitous, found in the highest levels of government and the private sector. But they failed to understand just how out of place the neon bits of paper would be sailing about outdoors. One of many swarming object photographs from Thomas Jackson's Emergent Behavior series.
The forgetful time travelers kept their ship cloaked at all times as they leaped from past event to past event. They kept post it notes all over the interior of their ship to remind themselves of daily tasks and research. Unfortunately they did not realize that it interfered with the cloaking ability and anything touching the hull directly would be visible to the outside.