A puzzle that the players fail to solve, or a hidden thing that they fail to find can lead to dead ends or frustration if they are essential to the plot of an adventure. When writing an adventure that includes puzzles or hidden things, you need to ask the question: What if the heroes never solve/find this?
You need to have an answer that allows them to still complete the adventure. You can make it a bit more difficult, but it still has to be possible.
The other thing to consider is how much effort and coolness you put into the secret thing. If it's something you're itching for them to discover so that you can bask in the glow of their appreciation of how awesome it is, you need to give them better/multiple chances to actually discover it!
Commentary by memnarch (who has not seen the movie)
If the GM wanted to poke fun at Pete, they could have made something up like "like the puzzle of how to get Nute removed from Artoo on his own?" or similar. Can't go back and solve that puzzle now, now can you Pete!
Hmmm. I can't tell if this is a pan out shot that we'd left behind from when we'd seen Rey last or if they're edited to remove her somehow with the text bubbles covering up the edits. Neither seems plausible; editing the images is time intensive and rare so far, but why would the movie have 3 different views to show that she's no longer climbing down the wall? They could also be zoomed in clips from that scene I suppose, but the image clarity seems a bit too sharp for that.
GM: Back to Rey. You can’t see any other exit from the coffin.
Rey: Search for secret doors.
GM: Uh... <roll>... you don’t find any. It looks like a wiring access niche.
Rey: As far as I can tell.
GM: As far as you can tell, yes.
Rey: So there could be another way out.
GM: If you have no awareness of any, does it make any difference?
Rey: I’ll have failed to solve the puzzle.
GM: But you won’t even know.
Rey: But you’ll know!
GM: I’m not telling anyone.
Rey: You’ll be smug in your secret knowledge that you defeated me.
GM: If nobody knows that I’m smug in my secret knowledge that I defeated you, does it matter?
GM: Let me just write a note to myself to include undetectable impossible puzzles in every situation from now on...