If the repair is such that it melted the vinyl, the best repair is to 'cut in' a replacement piece. You'll need a scrap of flooring from the original install, or you'll need to take a 'piece' out of a closet or something, to do this job. In either case, you may have a color difference since one came from being stored down the basement or the other came from a dark closet. At worst, if you can find out who installed the floor or who mfgred. it, maybe you can get someone to get you a scrap piece.
Once you have a piece, make sure it's what you want to use. (Matching-wise ...) Then, go to How To Repair Vinyl FLooring to see what you have to do. Make sure you work with a big enough piece of scrap AND you use a NEW blade to cut. If you can get a couple of good sized scraps, that would be best.