Awww, you've gone

(Or worked out how to make yourself invisible)

Hmm, so who could it be

Thymy: No, too coherent
Futt: Possible, but I dont think so
Death: Naaah, too obvious
Sally@ Naaah, too Old
Rangarig: Tooo busy posing
Taggart: too nice

So that leaves, Jack............

It would be down his alley, he has the knowledge and the technique to pull it off

Or it could have been the Butler