I just noticed the other day that the emergency key fell out of the back of my key.

Does anyone know where the best, least expensive place is to get that one key replaced? or do I need to replace both sets of keys?

I've backtracked all my steps and still no luck on finding it. I still have the other one from the other set of keys. Is there need to panic and replace asap or just pay the price when I return the car?