I think your trying to be to logical about this and i refer you to the example given by umbram further up in this thread about ring/frogs but ill go a little further.
Say you lived in a world dominated by midgets, so say our world but you and a select group of about 100 are still 6-7ft and can fly but the rest of us are say 2-4ft and one of has snuck into your home whilst you where away, slew your wife and stole your child. Would you -
1. Seek logical clues to the whereabouts of your child
2. Look for others of your race facing the same issue
3. Start killing every midget in sight till one of them found your child?
I think the issue here is your overestimating the difference between us and dragons. Yes their fiercely intelligent and hold different values to a human, but im pretty sure in your scenario theyd just go crazy and start attacking every town in sight till some one brought them there dam child.
My theory is party in supported by more notable names in the return to caves of chaos. In witch this very scenario is used as the kobolds are housing an egg belonging to some bronze dragons, who (somehow) have tracked the egg to the area of the keep and i can assure you their not clever or subtle about the way they go about getting it back. Infact they fly straight into the middle of the keep and announce people are going to start dieing if their baby doesn't come back soon whether they stole it or not. Id like to think my mum would do the same for me, even tho ironically she probably wouldn't.
You're right to a certain extent. The Green dragon did just that: headed for the nearest town and wiped it out. The local authorities summoned adventurers and they eventually killed the Green.
The Black Dragon DID in fact fly to the nearest town and confront the human representative of the Cult of the Dragon. Why? Because had had reason to believe that only he knew where his lair was. He proceeded to thrash him, got the name of his superior in the COD in Waterdeep from him.
During the attack, he was being observed by the two Gold Dragons who had tracked their missing eggs to the same man but who had not, as yet, moved overtly. The Golds lose their lead on their eggs with the death of the COD contact and the Black has a name in Waterdeep. The Golds reveal themselves but are unable to converse with the Black because of his rage. They battle and, eventually, end up over Waterdeep. (see the scene described above.)
The Black is chased away by the Golds and calms down a bit. He moves his stuff to a new lair (treasure first), leaves a note swearing vengeance in his cave (burned into the wall with acid), says goodbye to his mate and begins his search. The Black is smart enough to understand that a frontal attack on Waterdeep will give nothing. He will die and, besides, how do you find one specific insect in an insect hive?
Here is where the different psychologies of dragons kick in. Logically, he could just put on a show, land at the gates of Waterdeep and wait for a delegation. He then tells them his story and demands that so-and-so be handed over NOW or suffer the consequences. Assuming they could find the man, the Lords would comply knowing full well that Waterdeep COULD win against the dragon but at great cost.
However, dragons don't think that way and especially evil ones. Parley with insects?!?! Never. He will find the individual, he will wring the information from him and he will find the thief. Once the thief is found, or his location determined with enough certainty to satisfy him, THEN he will wipe out whatever town or city harbours the thief, be it Waterdeep or something else. He will not, however, spend himself uselessly. It's the thief that must suffer, not his lackeys.
This is where the group comes in. If the Golds ask the group to speak with the Black dragon and the Golds tell the group to explain the spell known as Discern Location and promise to help the Black find the eggs, THEN the Black might be willing to listen. I plan on giving the group some sort of traditional dragon words for parley or 5-minute reprieve, kinda of a White flag for dragons, to ensure that the Black will wait before destroying them.
That way, they get to use a host of skills they don't usually use, the "diplomacy first" bard gets to have fun, the arrogant half-orc gets to be slapped down etc. Essentially, a great role-playing experience of talking to a pissed off dragon who desperately needs to kill something.
I also get to have a "lightning in a bottle" situation where two gold dragons have to cooperate with a desperate, grieving black dragon using the group as messengers. Meanwhile, the group is dodging assassins from a nopble they pissed off, the Shadow Thieves who want an artifact they have ( a horned ring) and their own day-to-day preoccupations. Fun all around.