In my experience and from what I have read and heard, the tongue will only be lost if the chameleon's tongue is so "weak" that it loses its ability to retract completely down into the floor of the chameleon's mouth or if when the tongue is extended it can't be retracted and dries out.
I have had a couple of chameleons that have had their tongues amputated over the 15 years that I have been keeping chameleons. It was always due to accidents and not any health issues. They can learn to eat without their tongue, and if they have enough "will to live" they will live a normal lengthedlife. They just have to learn that they have to pursue the insect like other lizards do. They have to be hand fed until they can learn that.
The vet visit is still a good idea because the vet should be able to help you figure out what to do to correct the problem.
Hope all goes well!