The airline won't know to be honest, the checkin agent certainly won't.
It all depends on the policy in Dublin in the baggage bays. Even if the system is butchered to give a through baggage if it gets trapped even if its listed against your ticket number it still won't make the aircraft. None of the crew will know if its on board or not, the only way of finding out would be to get hold of the bingo card from the baggage crew leader or physically watch it go on.
And if your bag doesn't turn up in Donegal don't be surprised if you get told to deal with Dublin.
And the other thing is your getting off an international flight from the middle east so your going to have to clear passport control and customs as its your first entry port into the EU. You won't be able to just internal transfer airside. Donegal isn't an international entry airport I don't think unless notified before hand and the BE flight will be classed as internal.
Also as well that flight is going onto Scotland so you will have to clear the Irish-UK security stuff.
Don't be surprised if trying to force your bag through doesn't set off a load of security protocols for both smuggling and terrorism.
Customs & Immigration
Seems to confirm what I think will happen.
So your on a none starter anyway.