He'd have thought it would be a lot louder in Richie's mindscape - like the constant beep beep bloop of game soundtracks, the jingle-jangle of tokens, background music that was all clanging and banging. But it was actually sort of quiet (filled with more white noise than anything else), just not organized in a way Dan would have anticipated.
But it wasn't his head. It was Richie's - and yes, he had his own methods of recollection and retention.
You remember where everything is? Dan asked, though he assumed that was the case. A messy room could look like a hurricane ripped through, to the average person, but to someone else it was an exact science. We should find...you know. The parts that are cracked, that have been filled in with something else. The dark stuff.
It would likely be where the Shine was, tucked away and dormant. One of those televisions, needing to be tuned to the correct frequency.