If the piece was big enough to not float away, you could just place the cutting on a rock or even in the sand. Hardest thing I find about frags is keeping them where you put them. Even if you attach to a small rock, hermits, fish, etc. will knock them over.
I would also run carbon if you don't already after fragging. This will help with some of the chemicals released after fragging. Fragging outside the tank is always best but sometimes can't be helped.
With star polyps, I like to keep them sequestered. They will overtake anything in their path.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,