A half dozen press-on patches... and a stamp sized sanding/roughing thingy? That isn't a big savings. And whatever killed the flat tire was likely ran over by both of your tires.

I keep my spare tube in a large bag (folded around the new tube). When I have a rare flat I use the new tube and put the old dirty tube in the bag. If I have a 2nd flat before replacing the tube... at least I can patch the flat tube.