I had a Starling come down the chimney, but it was stuck inside the wood burning stove. There was still hot ash in it, too, from the night before so it's lucky it didn't get hurt or die. I came home from work and heard something in there. I was afraid to open the door thinking it must be a squirrel, lol! Well, I finally opened it and out flew the bird. I opened the door, chased it over there, and it would land on top, but not fly back outside. I'd go closer trying to shoo it out the door and instead it would fly all the way across the house and into the kitchen. We probably went back and forth between the door and kitchen 6 or 7 times before it finally flew out the door.
My parents once had an owl come down their chimney. The screen in front of the fireplace kept it in, but they had to get a blanket around it to catch it and release it outside.
5 days of a frightened Myna bird was probably a horrible mess. It just figures it happened while you were away.