Vodafone can't because they'd need the owner's permission to access their stuff (yes, they'd need their permission to find out how to ask him for permission). Plus, there's no reason why they should.
You can report it to ebay, since whiever sold it was doing so fraudulantly, although if it was sold as nonfunctional it's more gray area if you'd get refunded, but the one who sold it needs a clip round the ear.
Even if the owner didn't file it as stolen, the fact there's a blacklist could mean they reported it to vodafone but didn't have insurance so didn't follow it up; the phone was stolen from a shipment or lost in transit so Vodafone blocked it; it was taken out as part if a fraudulent account so blacklisted by Vodafone when they couldn't get it back from the criminal; it was lost, not stolen, so no need for police intervention, but simeib found it and decided to make a quick few quid. Many reasons, all of which end up with whoever sold it to you having no right to do so.
