A good photo of the damage would be an extremely good place to start!

I would also suggest visiting the plant at random times of the day in an attempt to catch any critters in progress- dawn is a good time to start.
It is my opinion that treating for pests without a solid ID can be very futile as well as ultimately damaging to the plant in question.

I have had very good success forwarding photos (or taking a piece of the damaged area) to my local cooperative extension office. They are quite familiar with all the pests and other maladies prevalent in your area. You can find them in the white pages listed by county.
They are an overlooked resource IMO.

At last a picture of the leaf damage! I'm hoping there's a spray remedy or some such as I have trouble getting up after I've gotten down!

That's weevil damage, and they are night feeders. You need to go out at dusk and later, after dark, to hand pick if choosing that control...

Here is a link that might be useful: weevils - rhododendron

Thank you. Now I know what I'm dealing with.