Most of the time when they don't come back there's good reason for it. Antonee Robinson is one of the few that in hindsight it feels like a mistake to have let go. But we were shopping in a more premium place back then. Robinson was trying to break in during the back end of Baines career and the first few seasons of Digne. He wasn't good enough for us then, but of course I'd take him now (I still think Myko would be my preferred starter though).
And also, to throw an example of a loan being beneficial. You have Branthwaite.