Maybe the other person in the pair is forgetting to use their tools because they are stressed out by the aggressive person standing over their shoulder looking for any excuse to grab the keyboard?
Mostly I think the exploratory phase of debugging is a battle between your limited short term memory and your imagination. It's a think you need to do alone and without someone stopping you to ask why every fifteen seconds. I think that's why people are so big on repro steps, so they can go off and start the process of elimination without having to dump state while defending checking possibility A before checking possibility B.
I think the only reason (besides tenacity) that I fix bugs that others gave up on is that I have tricks that let me walk the code faster, which lets me make forward progress on deduction before I forget WHY I was looking under this rock in the first place. My debugging practices look not unlike a guy looking for his missing keys. You have to be careful about when to hit him for questions, and most of the time it's better to just start your own parallel search if you want to help.
There's nothing quite as deflating as finally getting to the end of diagnosing a particularly pernicious bug just to have the understanding trigger the realization that you've encountered this bug before a year or two prior, spent just as much time originally figuring it out, and had somehow forgotten about it the interim. Yay for wasted days of our lives.
I think I need to make a concerted effort to get more sleep.
// time spent = 30
Personally, when I find out / solve something tricky I note down the details in a notes file exactly for cases like this. I'm yet to use it though, because I usually remember the weirder bugs I've seen.
Already in late 90's I couldn't believe what UNIX coders considered state of art, versus what we had on Mac/Windows/Amiga environments (the ones I knew before UNIX).