Cat Got Locked in Shed

I have two outdoor cats that are about a year old. Before anyone starts, I live in a camper with two dogs and a cat already, and these two girls showed up here about a year ago. We have a large abandoned house on the property they mostly keep to, so they have shelter and an insulated cat house inside. They get fed and watered twice a day and routinely checked on. They've never even had a tick.

My boyfriend has a box trailer he works out of like a workshop. He was in there the day before yesterday working. I told him to TRIPLE check before closing it, and he did, but Nami is a quiet, sneaky girl and I guess she was inside.

I couldn't find her yesterday but, again, she's a sneaky one so it's not that uncommon to not see her for a while. What concerned me is when I still didn't see her this morning. So I went looking, and my dog was really interested in the trailer, and sure enough, out she came.

She had a HUGE glob of yellow snot stuck to her nose and her left cheek looks swollen. She's otherwise normal. She's eating but not drinking. She can breathe through her nose but occasionally opens her mouth. She's making congested noises.

The vet doesn't open for another half hour, I've already left a message. Just wondering what I can expect and what I can do for her before the vet opens up. She's stuck to my hip now and I'm afraid to leave her alone for a second.