Most likely scenario is that you heated up the voice coil to the point where the varnish that seals the voice coil cooked. That is why the smell is probably somewhat like burning plastic. Worst case is that you would just replace the driver. But, if you are not the nervous type, and the speaker does not sound any different, you probably did minimal damage and should forget about the whole ordeal. If you go this route and eventually sell the speaker on this site, it would be necessary to cover this ground in your ad, however. BTW didn't anyone ever tell you not to smoke while doin' coke!