The last mobile phone with a metal chassis was dropped from high altitude to destroy a gun emplacement during the second Gulf war.

Modern phones simply do not usually have a metal chassis, the absence of which contributes to their light weight.

If you remove the battery from your phone you will typically discover that it has four electrical connectors, not the two that one would expect. The extra two are used for battery management.

From this we can conclude that mobile phone batteries contain WIRES, which if one is terribly smart and does not upset the circuitry, can be used as an antenna. This is similar to the technique for using headphone connecting leads as an aerial in small radios.

Risto Savolainen is doubtless biting his tongue, at least gently.

That's my guess.