I agree with piplup, if someone excuses their lack of work with that they aren't allowed to be near sharp objects unattended, no matter whether I'd think it's true or not, I'd take the head back and would have asked for a partial refund, both out of courtesy towards the artist and for the sake of myself.
If the excuse is true, then they are likely going through a serious issue in their life, and if you suspect they're lying then you'd be better off to move your business elsewhere anyway.

Also they mark their age as 14-18 meaning that they're probably underage and generally I wouldn't do business transactions like this with younger kids anyway since they usually may lack the needed professionalism and experience (like, leaving the head to other parent's house).

I'd suggest you just go and ask them to send the head back.