Just consider that you've fed a whole lot of mice for the next few weeks ...
Is it the just the inside bag or the box as well?
If it's just the bag then the vacuum might work.
If it's in the box and it's upright, a coat hanger hook (or bent nail) on the end of a long broom stick (or 2) may do the trick.
If the bag is quite full and in the box, just wedging a pole (broom) between the bag and the inside the box may be enough.
I suspect your issue will be the 2.5m drop and the room you have above that space to manoeuvre.
Throw on some beers and fire up the BBQ and we can all come around to help ...

Dunno, I’m just an idiot.
I’m only the administrator of the estate of dedja … my yes be yes, my no be no