Clutchcargo once bubbled...
Yup, you don't have to tell me, I always tell her to please leave the ring in the room. One of the things I hate saying is "I told you so."
Not nearly as much as she will hate hearing it from you, and not even remotely as much as you will hate her reaction to your saying it to her. Take it from a guy who has survived 21 years of wedded bliss: suffer the loss along with her.
Don't replace the ring, though; you've done your part when you bought it, and there's no reason to throw yourselves beneath the wheels of an added financial burden you can't afford. It will hurt more than it helps in the long run.
Hopefully the value of having each other as soulmates far outstrips the worth of the lost ring. Tell her that (without the "hopefully" of course) soulfully, looking her in the eye, over a moderately expensive romantic dinner (before the third glass of wine), and get past this bump in the road.