If the indicator dial isn't turning then its more then likely snapped and broken inside as they don't usually just fall off like this.
Now you can open these up so if hubbie is good at fixing stuff he should be fine.
You need to remove the top and then pull out the soap drawer.
From there remove the screws on the inside were the soap drawer goes.
Then you need to remove the frame. From memory on these they are clipped in from the top so you need to prise it out with a small flat screwdriver.
But just look on the right hand side of the panel first as some models have screws on there.
With this off you will be able to see whats broken from there or weather its come off.
But looking at the parts list for the indicator disc I think its obsolete so no longer available. so worth try to see if your hubbie can somehow fix it back on.
So check that out and see what you find. But yes you just need to remove the front plastic frame and you can access it all from there.