A slightly warped pan will perform the same as a flat pan on gas from an efficiency perspective, the shape isn't going to waste energy. As for whether the warp will impact your cooking experience it's hard to say, a warp can cause coatings to flake off, or make liquids pool in or run away from particular spots.
You do not need to throw out the pan
Metals tend to be impervious to absorption of much in the way of plastics (or anything else), which is part of the reason they make great cooking implements.
If the plastic is on the cooking surface and that surface was seasoned, to be absolutely sure, I would recommend that you remove the seasoning and re-season.
I accidentally left a aluminum sheet pan in the oven during the cleaning cycle. It certainly cleaned it up nice and new looking, however, it altered the molecular strength of the aluminum. It made it softer and easy to bend. I decided to throw it away because I was not sure that it was safe anymore to cook food on it.