Oriah, I have a brilliant example of what happens when a person who is very shortsighted doesn't keep their glasses close at hand. In fact, I had three examples, but the other two are so badly damaged they've been thrown away.
The last pair I keep in the car, even though they only have one arm. I had to move the car to a car park today due to one of Mr Z's insane ideas, but decided it would be a great idea to tramp out in a foot or so of snow, in the pitch dark, with a dog and an ipad, to take a pic for you. Without my glasses, obviously. My internet connection had gone down so I wasn't busy.
I have a wet dog, an even wetter ipad, a frozen hand from trying (and not succeeding) to get the snow off the car so I could get in it....but I don't have the picture.
After all that I had an idea though. Wouldn't it be a simple idea to go through Bob's receipts? I'll eat my hat if he didn't keep receipts/maybe insurance claims for his glasses. Count the number of receipts, detract the number from the number of glasses in the house, and that should show if any are missing.
I've broken dozens of pairs of glasses. Only once was it the lens. Every other time an arm has broken off, or been so bent at the hinge they are uncomfortable to wear. It's easy to see when that's happened; hold them up sideways on, and you can see if one arm is really out of line. Even if the arm's pushed back into shape, the hinge usually has a crack or bend that is still obvious.