How frightening this is when any dog gets lost but worse when it is a senior.
With an older dog like this they can get confused and lost much like a senior person could.
I am not 100% sure animals 'run off to die' as much as they might have a sudden medical incident while away from their usual area, or that they might get confused and not be able to find their way home even from a familiar area.
She may have pursued that delicous smell and then realized she was lost. She could have gone into the woods and become stuck (collars can do that) or had that be the time an aneurysm burst or a blood clot hit her heart or lungs etc. causing her to pass in an out of sight area. Accidents such as a fall into an area a dog can't get out of (an old well for example or a rocky area) or being locked in a building by someone who didn't know she had entered are other possibilities.
If you have a friend with a dog that she knew you might find her by running another dog in the area. She might respond to the dog or the dog might find her or her body.
I'd suggest making up a picture poster of her if you can and give it to all the neighbors plus post it at the local store area and with local vets, mail carriers, and police in your area asking to be notified if she is seen.
Post a lost notice on www.craigslist.org in the pets area and check it for any found notices. www.petfinder.com has an area where you can post missing pets in the classified ads area too.
As she is deaf and can't hear your calls you might try making some strong scent posts to try to lure her to them so you can find her. Take sweaty socks or t-shirts and soak in a bucket of water overnight. Then use the water to make scent marks along a trail to help her nose find you if she is out there wandering.
But with her heart issue it may be that she passed on while out there enjoying herself but out of your view.
I would keep the search up for another week and then if there have been no sightings of her you may have to decide she passed on while out having her fun walk with you.
I can tell you I got one dog back after she was missing three weeks in the country side (scent markers kept her in an area where we finally found her 3 miles from home) and posters got me back my missing cat after 6 weeks when she was 5 miles from home!
Even out in the country neighbors may see what you miss so the more you notify the better odds that someone might see something to help you find her or at least find her remains so you don't have to worry any more.
I hope this helps you!