You've done the right thing, and yes someone could have pre-hijacked it.
If you go to your domain panel and add abc.com (literally, try it) you'll get a warning that abc.com is already in the system or somesuch. If you had tried adding your friend's domain and had received that error, that's when things might have gone astray. If someone else had previously added your friend's domain to their userspace you'd have to get in touch with Support and get them to sort it out before changing the NameServers. But they haven't, so it's all good
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