Probably not the necklace? She already knew that Amano had forgotten it at another girl's place, so it wouldn't make sense to assume she's there just because the necklace is.
Chiwa has no idea that Yuhi left the necklace at Sakurako's apartment. When asked by Chiwa about the missing necklace Yuhi's only response was "Just a change of pace...maybe?" So, she might just assume that Yuhi decided not to wear the necklace that day. In fact, for Chiwa to tag an item of Yuhi's, she would've picked an item she would be certain Yuhi would have on her at all times. Considering she noted that Yuhi didn't take the necklace off previously even during sex, it's possible it was the chosen item as it would've been seen as the safest bet at the time.
Which leads to an issue, since the necklace always seeming to be in Sakurako's apartment is giving the impression that Yuhi's with Sakurako even more than she actually is, which is further driving Chiwa's anger.
