I like this sticker but where would you put it? I wouldn't want to put it anywhere visible because it is ugly lol.You did what you were supposed to do. Any problems that arise as a result of the tow should not be your responsibility.
In the mean-time you should get one of these: AWD Flatbed Tow Only Acrylic Decal - Subie Stickers
Hopefully there won't be any issues. Good luck with it all.