I hope he's doing better.
Don't jump to conclusions. If you have a good doc, let him do his job. Just give them a little time to figure out what happened. It takes a lot of tests to put all the pieces together sometimes. We are all different. People spikes temps all the time from stuff like this. It doesn't mean he got something from the hospital. Even if he is positive for something, it most likely didn't come from there. It doesn't show up that quickly and manifest that fast usually. You are more likely to get something from the cart at the grocery store.
Just a question... did he go to the dentist or have any dental problems lately? Like even a bleeding gum from flossing? Or even if he has a bad cavity or something. If so, let them know that. It really is important. Staph and other infections that create heart problems can come from the mouth very easily. I know it sounds weird, but it's true.
Good luck. waiting on some good news from your side.