If a character has 3-4 lines in a short film...?

[Rowan]

How short is the film? Really, it depends on how important the part was to the film as a whole. If it was just the CD salesman who said "Oh, you'll want to buy a player too, miss", then it's a bit part. If the entire film was just a few minutes and the 3-4 lines were those of the main character's crucial best friend, then it counts as a supporting role, or you could maybe fudge it into featuring.

Honestly, I'm not sure what else you're asking. Do you mean you want to reconnect to old friends and colleagues? Facebook, email, and reunions organized by whatever third party you have in common are the easiest ways to get back in touch.