If someone got in and took your keys (way back when) they either had taken copies or got into your house some other way.
(Why would anyone be able to take copies? Did you give them your house keys at the time?)
If they used copies of your keys to get in, why would they need to steal more keys?
Did that key set have your car keys on it? (TIP- never have all your keys together.)
Why would they abandon your set of keys on a bus? What was the point in stealing them only to leave them on a bus?
That implies they wanted them to be found. Usually burglars chuck them under a bush or something.
And the person who found them- could he be the thief?
None of it makes sense.
Ass PPs say you need security, motion-detection lights, cameras (not doorbell ones) on your house where no one can reach them, and a burglar alarm.
My instinct is this is someone playing silly buggers. If they really wanted to burgle your house, they would have by now.