I think 3 weeks, even in a fridge, may be pushing it a bit, but mainly it would have needed turning regular, but depending on how you were planning on incubating it, what have you got to lose? If it's one of their offspring you are wanting I'd give it a go.
When they are laying I suppose it could be a couple of weeks before 1st egg and starting to sit.
But you would be best getting some more as well, if it did hatch, not fair for it to be on its own.
Good luck
Sorry to hear about your geese, mine are fastened in every night, did forget some last night, luckily all OK.
Had them attacked twice in daylight, luckily we saw wing flapping and saved them.