Of course the hash when you click the button is going to pertain to all previous rolls but if you dont click the button you dont see the hash, when you click it then the site can chose a hash that pertains to all previous rolls and you would think they are legit
I doubt any dice site has that kind of computational power no matter how much they've earned. It would be like trying to use vanitygen to get 1UNPOSS1BLEADDRESS1234567890 and expecting it to happen instantly.
No uppercase 'o'.
Yes, really

No lowercase 'L', no uppercase 'o', no uppercase 'i' and no '0' (number zero).
If you used -i (case insensitive) it would have looked for 1koeLen (and 1KoeLen and 1KOeLen and 1KOELen, etc. etc.) - but the number it should have returned should have been very low then (as there's many more possible hits). If you used it with the -r (regex), then I think it accepts all those forbidden characters, but it wouldn't give an estimate of when it would be found (if I recall that correct).