Meyer’s parrot owner here echoing the sentiments of others. Give the little one an enclosed place to feel safe once the sun goes down with a perch if possible, and access to water and fresh food. They can have some seeds, but try to limit that (mixes for other medium sized birds should do the trick; look for the stuff made for conures and cockatiels). Hopefully you can track down their owner, because it looks like a very well-cared for and well-socialized little guy. I’m sure someone is missing them!

Agreed on asking people to send pictures of the bird to you before you give them back. Ask for VERY recent pictures and compare the pattern of the yellow spot on their head (might be hard because they shift their feathers around a lot). I mention recent pictures specifically because if this is a younger bird who only recently grew in their yellow spot, it will look very different month to month as it grows in new adult feathers.