Its a mystery

I let a kit of 4 out on Thursday it was lovely clear blue sky they were going for about 50 minutes I looked up there's one pigeon left flying so I assumed maybe a hawk had chased them and they went down to hide away . So I got the one remaining bird down
Sat waiting for there other 3 but they didn't show up . Thought there safe some where and will return next morning . Came home from work no sign and I haven't seen them since so unless a plane hit them I am really lost for answer's .