Well, sorry, I found my problem. The issue was the events order. The target was reset to 0 then further down in the event sheet, set back to the UID of the destroyed Friend.
Which is strange since the Friend was destroyed before Foe's target would be set, so I don't understand why Foes detected the destroyed Friend.
Anyway, I put the target reset logic at the bottom of the sheet to fix it. But I hate not understanding something