I havent seen any tricks to finding tanks, just comes with experience of figuring out where their spawn is, then drawing a logical driving line from there to their logical target. Fly low and look under the trees. Some are just impossible to see if they are in bushes that cover them.
However, if they are attacking with 15 people I seriously doubt anyone looked at the film, that would require them to end their current sortie, go watch the film, then take off again and fly to that base. More than likely someone just saw you. And if you were the sole defender at the port its probably safe to assume you had eyes on the maproom, which also helps attackers to be able to find you, process of elimination of the view points.
