1) maybe it was an accident, we are all human after all, satoshi wasn't a god, it can happen
2) this will only reinforces the first point
3) i don't think he is talking about aan altcoin, most likely completely different than bitcoin, not based on blockchain or something, otherwise it would be stupid for him to build a pure clone...
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1) No. Satoshi has so many addresses which most likely extend over several wallets. Losing 1 or two is acceptable, losing all of them isn't.
Besides, who does not have a backup of their encrypted wallet somewhere?
2) 3) Satoshi claimed that he is moving onto different projects when he contacted Gavin the last time. This is only natural.
However, I doubt that he is sticking around and wasting his time on some altcoin.