Sad to say, pretty much everyone who wants to get a snake shipped should do enough homework to know that shipping UPS is in fact, illegal.
As well as wanting to know where the snake went, I'd ask UPS about filing a complaint against the seller. After all he/she knowingly broke the law.
As to your claim of someone there knowing there was a snake inside and deciding to steal it, that is far-fetched at best. Unless the box was plainly labeled as containing a snake, how would anyone know what was in it? And just as Judy said, if it were labeled as containing a snake, why on earth did they accept the box in the first place ?
I'd be a lot more concerned about why on earth a seller was using UPS in the first place, since they should ALL know not to do that. That would be the equivalent of shipping a pipe bomb through the post office in a box labeled "explosives". No body in their right mind would try it.
So I'd be contacting that seller, and demanding to know why they used an illegal shipping method. If that method was stated in the ad, then I'm sorry to say, you should have done some more research. I'd never accept a live animal being shipped to me unless I knew for a fact it was being sent to me legally and safely.
Gale