I've found a part workaround - put a space. This has pros and cons:
- a space keeps the drop down menu (your own description doesn't) and;
- when users click on the textbox, the space is highlighted enabling overwriting without the need to delete the space first.
- the space highlights everything that has a space, no this may not be a good solution if your descriptions have spaces.
If you know the answer, do post it here.