not to sound mean or anything but with any animals (or childern for that matter) around the house you should lock doors up and put your projects up as high as you can...i've lost many parts in the past from my nieces and nephews getting into my unfinished kits (and even more into my finished kits ) now if i build or paint something, it's usually in a place they can't get into...like in an extra room or the garage...
with that said...i would just continue building the kit without the head...you could say it's a demo version of the VF-0S ...but that's just me...i suck at sculpting so i wouldn't resulpt one...if you have the skill and time to resculpt a head then by all means do so...but it seems like you're strapped for time so maybe it would be a bad idea to do it at this point in time...you could also ask for a head here on the boards or order the tree the head was on from HLJ or any other online store that does parts requests...
wish you luck on your kit