It is highly unlikely that any bulbs that have been out of the ground for two years are still viable. If you can find them and they are viable, they would be sprouting by now. Otherwise, leave them where they are for compost. The ones you planted last year are your best hope for anything from that batch. Bulbs are living things. And although they will survive outside the ground under the right conditions for a good while, two years is way outside the realm.

If I bring the unplanted ones back inside, will they start to sprout?
I second what Donna said above about it being unlikely that they would still be viable.

Just to make sure, you could squeeze them, to see if they were totally dried out, or else gone to just 'mush, in the center. If there appears to be any firmness left, I'd suggest cutting a few open, cutting from the top of the bulb, down through the bottom, basal plate.

Chances are you will find that they are just no longer any good. Please let us know what you find.

Sue