I'm not sure you can logically determine the type of previous owners this bird has had by the fact that he is scared and quiet.
He did just get rescued from being out in the wild and you are new to him. as with most captive breed animals, I would expect that an escape to the big outdoors might seem inviting. However, finding out that there is no one to feed you and water you and that, quite possibly, there are things out there that want to eat you ... just might be enought o scare the sqwawk out of you. Then add to that a new face, new cage and new surroundings. What's a bird to think?
Keep an eye out for local flyers and notifications. THere just might be some unhappy former bird owners missing their baby!
Forbey