You walked into a tough situation, though. Resident of SNF? Age > 70? AMS is UTI or pneumonia until proven otherwise, right?
I'm currently reading The Gift of Fear, which puts a lot of emphasis on intuition. Your brain notices so much, way more details that you can consciously notice without having a routine that you go through. You went in with a suspicion based on knowledge and experience, and every detail you noticed confirmed, not denied that suspicion.
Imagine the same situation, where you went in and found the same thing: dispatched for AMS, at the nurses station you hear "UTI, AMS x 6 hours, foley with sediment, fever..." and then went into the room and found the patient to be a flaccid lump of a person, with gross pedal edema and a heart rate of 32. This would obviously get you thinking beyond the UTI, and quickly. And knowing what you do, you automatically would suspect that this is a dramatic change, because people who have been sick in bed for days don't really have hugely swollen feet, so he was likely up in a chair at some point today, which makes this a relatively new and dramatic change in his condition.
I'm willing to bet that you did a complete exam, knowing you to be an excellent clinician. So you heard nothing in his lungs (not pneumonia too...), what neuro exam you could get was at least symmetrical, pupils equal (not a CVA...), EKG normal (not an MI/cardiac issues), his sugar was normal (not hypoglycemia).
So you didn't strongly consider those issues, because they were extremely unlikely. But you "ruled out" those possibilities as reasonable suspicions.
Anyway. I'm arguing that a skilled clinician IS keeping the wider view, just more subconsciously than you realize.