If you load
this save, you'll find yourself parked next to a satellite, which is a target for a trade guild mission. The mission briefing doesn't state any time limit. Hang around for about 90 seconds. The satellite will disappear. The mission will disappear from the mission manager. There will be no entries about this in the log book, no messages on the event monitor.
If you look directly at the Satellite (e.g. it's highlighted), then the target brackets will remain for however long you don't move the view, even past the 90 seconds. But the satellite will be gone regardless.
First time I noticed guild mission disappearing I didn't have a save handy, and that was a bummer, it promised tasty rewards

(you can browse the log book, acceptance of the other guild mission should still be in there somewhere).