Is your machine making any noises suggesting that the insect or part of it is stuck in there, e.g. a buzz caused by a fan hitting the insect's body as it spins? If not, chances are that the bug was blown back out again by the fan(s).
Assuming the insect got in between the aluminum lower case and the black plastic strip at the base of the display, it was probably sucked in by the fan(s), passed through the cooling air duct, and was ejected below the display hinge where you wouldn't have seen it emerge. Its chances of surviving the trip would have been negligible, and though it's possible that it got lodged inside, unless it's substantially impeding the airflow or the fan(s), a single very small bug isn't likely to make any difference.