To be honest, I am amazed that most people posting in this thread seem to be giving a pass to the friend that lost the keys. Please keep in mind, I am not criticizing anyone taking that position, I just didn't expect the sentiment to fall that way.
Sure, ultimately, the OP is responsible for fixing things with his Mom. But as soon as his friend took the keys and agreed to move the car, he assumed the responsibility associated with said task. One aspect of that responsibility was returning the keys, which he didn't do.
Anyway, to each his own. I hope everything works out ok.
-KeithP
I agree with the above posters. YOU are responsible for the lost key, but if your friend is truly a friend, he will accept at least part of the responsibility to you for the replacement cost...and will pay up.
Not sure if this will be helpful to you, but I bought remotes and keys from this place and it was substantially less than the dealer: keylessride.com (they were streetkeys back when I bought from them about 5 years ago)
I had to take the keys and get them cut and programmed myself to a local locksmith (recommended by them), but it was well worth the hassle. The two fobs and keys still work today on the original batteries.