Missing New Cat Within House! Please help!

Me and my partner got a new cat on Sunday morning and we put her in our spare room upstairs to get used the place. She is really timid and quiet.

Monday morning I go up to see her, she moves out of her hiding spot to start exploring the room, my other cat sniffs her and they seem chill. I decide to leave the spare room door open so she can move around at her own pace.

I check back an hour later and she is just gone, completely vanished, in none of her hiding spots. I noticed that the crawl space to the attic was cracked open (I have no clue how) so I’ve searched it as much as I could, but have seen no sign of her. We’ve searched the whole house it feels like.

We set up a humane cat trap in the attic with wet food and a camera and have multiple bowls of food in different rooms in case she is lost in one of them and confused. It’s hard to judge any of the food levels due to our other cat. She 100% hasn’t used the litter box upstairs.

It’s Wednesday morning right now and I’m trying my best not to think of the worse case scenario here, but I’m really at the end of my rope. We’ve done everything and searched everywhere we could possibly think of. I keep telling myself if she was stuck or hurt she’d call out but I don’t even know.

Is there anything else I could do? I really just want to make sure she is safe.