The sample isn't listed in the album credits or production notes for the song, and given Timbaland's history, I wouldn't be surprised if he did steal it.

Now, whether Utada would be implicated in the act via association is up to debate. I'd like to think not; it was Timbaland that did production on that song and it's not unlikely that, presuming Hikki was even aware he had looped that sample in before it was finalized, she likely thought he had full rights to use it. Keep in mind that when Utada sampled Ryuichi Sakamoto's piano melody for "Merry Christmas Mr. Lawrence - FYI" she gave full credit (the song itself is actually listed as being composed by Sakamoto in the production notes). Similarly, she sampled "Paint It Black" by The Rolling Stones for "Amai Wana (Paint It Black) on First Love, for which they were likewise credited. HER history shows that she's not the type to disregard copyright; Timbaland is another story.

That being said, for everyone singling out Timbaland as if he's some peculiar example of this in pop music, it's really not just him. I would say most if not all major pop stars in America have engaged in "plagiarism" of some form or another (and there's long been evidence floating around to support that speculation, feel free to seek it out)-that's what happens when you have a music industry in which the actual songwriting process isn't in the hands of individual artists, rather a comparatively small community of solicited producers and mixers that are constantly sharing with and taking from one another in order to facilitate a fairly uniform sound that fits the trend of whatever musical era they're paid to cater to. Timbaland just likes to overstep his bounds and steal from artists who actually care about and, occasionally, write their own songs, causing them to take action against him where no faceless behind-the-scenes music developer would. They're paid enough to stay quiet and rehash the same material every time a new potential starlet gets auctioned off to the music market; which really wouldn't exist as such if it weren't for this cannibalistic protocol (to be fair, this is true for many major music industries, including Japan; which is why Utada is such a treasure and a rarity, wherever she's active).

So, yes, Timbaland probably stole the sample. Welcome to pop culture. :/