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...
1
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.
1) losing does not mean only distractedly, but also because of some thief, no amount of backup will save you at that time
and not only cybernetic thief but also real life thief, many thing could happen that could steal your treasure