PLEASE HELP, Cat lost

I am so upset. My 5 yo calico Gracie must have snuck out of the house this morning when my husband left for work. She is an indoor cat and has never been outside before.
She is also a VERY timid cat who is scared of most things.

How do I find her and bring her back home?
I've left the back door open so she can wander in herself, but I'm afraid she is paralyzed with fear and hiding someplace.
Can anyone give me some suggestions?

UPDATE: post #6. We found her!!!!

Sit out side on a chair, reading and occasionally calling her name. she will find you if you stay put. Leave the door open while you are out there, because when you go to grab her she might run, and hopefully it will be into the house.

1st and foremost - DON'T panic!!!

Does she have a favourite treat that she will come running for? My cats come running as soon as I shake a jar of treats. I would walk slowly around the house calling her name (with treats in hand). She is probably hiding close to home, maybe in a bush or a clump of flowers. Does she have a cat bed instead that you can take out so she can see it or smell it. Try to put some tuna out, near the door she snuck out by. Hopefully she will be home soon. Please let us know when she returns.

Also put her carrier out by the door with a towel with your scent on it in the carrier.

If she's that scared, I'm sure she's close by and hiding in bushes, etc. Check cars (under the tire wells), garages, etc. Ask your neighbors to check their garages/sheds. Many times a cat will run in there and hide and the person closes the garage not knowing the cat is there.

Enlist in the neighbor kids to help search.

I can't really add much to what the others have already said.
Just wanted to say that she's more than likely "Hiding in plain sight".
Since she's never been out before she's probably very near to home, she could be under your porch or hiding in shrubs very close by if not right in your yard.

Sending vibes that she comes home soon.

Thankyou all for your suggestions. Gracie has been found !!!!!!

My kids and I ran around the neighborhood showing Gracie's picture to everyone. We were in tears, picking out the best photo to put on a LOST CAT flyer.

My husband took one more look through the house because he couldn't believe she could sneak out without any of us noticing her. Then he found Gracie in the back of one of my dresser drawers !!! Gracie never made a sound, she had to have been closed in that dresser for at least 10 hours.
I don't know how she got in there but I'm sure glad we found her...

I'm so happy that you found her.
They sure can sneek into some tiny little spaces.
Silly little things, but you gotta love them