reverse puzzling - What are they trying to solve?

I was on the the train once, bored as hell (because trains in Romania are really slow) and at one point I hear 2 guys behind me, probably as bored as I was, talking about puzzles.
And I thought:

"Oh! I like puzzles. I should join them. I'm sure they won't mind. But wait...what if I have no idea what's it about and I look like a fool? I better eavesdrop a bit and but in only if I know something".
But a window was open and the noise from outside covered part of their conversation.
All I could understand was this:

Guy1: Look at this (mmmmm). It has numbers and letters.
Guy2: it has to be a crossword.
Guy1: That's not possible because (mmmm). But they can be the moves for a Rubik cube.
Guy2: Pff...you're an (mmmm). There are only 6 letters in the Rubik cube moves. Maybe it's a matrix of something. Letters on (mmmm), numbers on (mmmm).
Guy1: Or a cipher? Man, I hate ciphers. Or a pattern?
Guy2: There are (mmmm), so this is probably not a rebus.

I this point I realized I have no idea what's this about and decided to shut up. Also, I'm a shy guy and I didn't ask them what's this about.
But I am still puzzled (pun intended). What was that about?

[Edit] In the light of the 2 answers I feel obligated to mention that the fact that letters and numbers are involved is not important.
And I remembered one of the guys saying at one point that they were trying to solve a puzzle from puzzling.stackexchange.com.
[/Edit]

Note: (mmmm) marks the parts I couldn't hear, but they are not really important. You can solve this without knowing what I missed. They are there only for dramatic effect.
Note 2: (not part of the puzzle, just "fun" fact): The trains in Romania are really, really slow.

Answer

Just from the OP's comment this is maybe too literal but

I suppose a possibility is that two guys in a train could be reading this puzzle now and making the same statements as in the puzzle. This may be too self-referential and hope ok to post.

I guess this could only happen after the puzzle has been posted unless the OP was present when it was being created, or that Romania time is ahead of mine, or being on a train reminds me of special relativity and the fact they are going slow may be be an observer's effect of near light speed travel - I've stretched too far now. I was set up to answer this by Marius :)