The same thing happened to me too!! When I went to bring Jubilee home, I found that the lady had chopped off parts of her mane AND forelock (!!!) because there were burrs in it!

Didn't bother to PULL them out, just cut them out! I was sooo glad she didn't go anywhere near her tail though ...
About the growing back, it probably does work the same way. Manes don't take that long to grow, its the tails that do. Work some MTG into it and it should grow in no time.