12 week old chick problem, HELP!

hi, picked up my chicken today and held it for a few secs. kept a firm grip as it was trying to flap so i lowered my hands and let it go about a foot off the floor. next thing the chicken flapped and lay down and clsoed it eyes and had some sort of spasm. i picked it up and saw it was still breathing, and after a minute or so it was ok again. anyone know of anything it could be, was it something i done? could it have problems in the future?

thx in advance for any help

i hope so, i thought id killed her and to top it off, she was dying in front of me.

update: found her dead in the coop today, she was slightly smaller, but wasnt getting picked on. hadnt been eating properly last couple of days. starting to think tht faint may have damagd her more than i thought.

  So sorry