I have a vol. lionfish that I bought awhile back that had one short fin. It will eventually grow back, but it takes awhile (my lions fins grew about 2 inches in about 2 months)
Just make sure that you feed nutrient enriched foods (silversides soaked in zoecon, zoe etc) and not goldfish. But you may have problems at first because lions tend to not readily eat frozen foods. But you may get lucky as I did with mine, it ate silversides as soon as I got it in my tank. Also dont have any fin nipping fish along with your volitans, like puffers.
About the fish being dropped?!? It could of caused internal damage. But for that price, it doesnt hurt to take a gamble especially considering its size.
The colors vary often times. When theyre pissed they turn really dark with their tips being a bright white color to deter other fishes away. They also swim in all sorts of positions (inverted, sideways...)
*also your damsels, and clown are in danger of being eaten. Being 4-5" lion, it has a BIG mouth! Mine is about 7", and the sucker ate my 2-3" clown tang!! gosh what an expensive meal!! But the wierd part of it is that he doesnt touch my two cleaner shrimps!!