Hmm, what was the device you had then?
If I remember correctly my very first "mobile" phone was Siemens nmt-910 which had a fixed antenna. Of course you cannot ever be totally sure (and I never disassembled it) but it looked like it was a functional piece.

The device that fascinated my cat was a Nokia 2110i which indeed has a retractable antenna whip on top of a helix stub.
This at least I am sure was a functional piece as I did take those devices apart several times.