Lost gift card? Plus a gift card that customer service says I can't use because it's too old.

I feel awful. My husband got me a $500 gift card and I can't find it anywhere. In my search through our house for the gift card, I found another random Nordstrom gift card in our files that may be it? It has a 16 digit number and 3 digit access code.

I called Customer Service to check the balance and they said the card is unusable because it's so old the access code digit system has changed (it should be 8 digits not 3). Is this true? I thought gift cards never expire.

If this in face the $500 gift card, can I use it in store? If it's not, is there a way I can get my $500 gift card replaced? Thanks.