There's a problem if someone is ACS defending a planet/moon of an account and that account gets deleted.

Player A [1:1:1] launches an ACS defend to Player B in [1:2:1], for example the flight time is 1h,
player B extends the duration with alliance depot for certain time (in this example, say 60 weeks), during this time player A can recall anytime and have fleet back at home in 1h,
if player B account gets deleted the fleet is automatically coming back from [::] for 60 weeks, there's no way to recall.

This is a bug, IMO, I think at least the fleet should still be ACS defending [::] instead of coming back from there; so the Recall button should be still available. Or may be, since the account gets deleted, may be the fleet appears instantly at home.

Or any solution you think of, but I think that having that fleet coming back without option to recall is not logical.

I said “I think at least the fleet should still be ACS defending [::]” but I see a problem with this: if some moon is popped and an attacking fleet gets redirected to [::] both shouldn't have a battle! I hope you have that in mind. Please, come back here once it's solved to explain the behaviour.