You're on to something here; I only use donated troops for defence, and my request was after I had been attacked but I still had some troops left.. subsequently those got lost in another attack so I requested more. Sadly it seems the Alliance I'm in is virtually comatose now so as I've had an unfulfilled request for troops open for days (!) despite me donating regularly, though I don't war. I'm going to have to find a new one..