How can a metal object bond to a live object when not touching anything else?
Although there is a earth connecting to the casing of the stove that does not warrant  that all parts of the casing are indeed well connected to earth. Frequently the extra earth wires are not or no longer well connected to the mainframe and therefore not earth properly. This leaves room for the current to flow along many ways and most probably the spoon has been in such a path making it welded against the casing. Since we can not see the actual situation more can not be said.