This is a continuation of the story started here.
It's been a crazy few weeks since you first deciphered Sam Smitherson's letter asking to meet at the Powell's Bookstore Café in Portland. You got to Portland the day he told you to, but being the absent minded type he is, he didn't tell you a specific time! Colorado Carl decided to show up around noon, but Sam wasn't there. When you asked one of the baristas if they had seen someone who matched his description, she pointed you to an empty table and mentioned something about him leaving with a tense man with a dark suit and sunglasses. There were a few pages and a red pen at the table, but Carl scooped everything up before you could get a look at them.
That was a week ago now, and for a while it didn't look like you were getting any closer to finding out what happened to Sam Smitherson. You've been staying in a hotel for the past week, and Carl has spent all his spare time poring over the papers Sam left behind. This morning, though, he didn't join you for breakfast like normal. After convincing the hotel staff to let you into his room, it appears he left in a haste.
You aren't sure if he left on his own or was forcibly taken. The room is a mess, but Carl has always been a bit disorganized, so there's no way of knowing if there was a struggle or not. The only things left behind were two of the sheets that Sam had left at Powell's, hastily stuffed inside one of the pillowcases. The papers are an old, coffee stained map of Powell's City of Books, and a handwritten list of some sort:
It's now up to you to find out where Sam Smitherson and Colorado Carl are! Best of luck!
Revision 1: Something seemed wrong when I was writing my last hint, and I realized that, somehow, a decent chunk of the information needed for the solution was missing. You should still know when you've found the right way to solve it, but when you get there, just add "PL6g" to your result, and that should clear things up.
You decide to test the pictures for various invisible inks, and your first test reveals more information, shown in blue. There are some numbers over various rooms on the map, and an extra note scribbled next to the book list.
After making some headway, you check the papers for any other abnormalities, and find some parts of the list are slightly indented, as if they were scratched on with a pen that had run out of ink. A careful rubbing generated the parts on the list marked in pink.
Everything required to solve this puzzle can be found in the images above. Thank you to M Oehm for transcribing the initial pictures. Additional hints will be provided every Wednesday and Saturday as needed