Messed up travel time - how to deal with it happening in real time?

Guys, I just messed up travel time. Players set out for location A and changed their course in favor of location B (further away), I slipped up and started describing the B location after they should have reached point A. Problem is, they know and they noticed... And time actually matters in this part of the story. How do I deal with that? Do I just retcon it and say "well, actually you don't see XYZ"? Do I make up something entirely different? I probably will retcon it a bit to make it work, but I'm curious to hear how you deal with slip ups like that (except for keeping notes, which I of course do).