Since they might not be good anymore, why not put the lid in the microwave with a little water so that it will soften, and then put the lid back on the container while it is still warm. Don't put the container in, since it is ok. Wait until the lid has cooled and see if it remolded. Or you could put it in a sink of really hot water for a while, until it softens. Since hot water or steam warped it in the first place, maybe the same will reform it if it is put back on the canister while it is soft. Duct tape it to the container to hold it in place?