Hayden Panettiere's engagement ring from former fiancé Wladimir Klitschko went missing days before her shock death at age 36.

The late actress, whose estranged mom surfaced this week, kept the sentimental piece of jewelry after the called-off engagement to Klitschko, now 50, in 2018.

Weeks after the star died of an accidental overdose on August 16, her loved ones have not been able to locate the ring, and believe it was taken from her.

'Hayden's engagement ring from Wlad that she's held onto for all this time is missing,'  a source told Us magazine. 

It was added: 'Friends and family think that someone who was with her in her final days took it when they were pawning her things.'

Panettiere and Klitschko, who were in an on-off relationship beginning in 2009, shared 11-year-old daughter Kaya.

The Montblanc ring, worth a reported $500,000, was designed alongside Panettiere herself.

'They made me this amazing book where they did a bunch of sketches,' she recalled to E! News in 2013. 'I told them my idea over time and tweaking things here and there, it came to fruition.'

The one-of-a-kind piece boasted a centered emerald-cut diamond and split-shank setting.  

Panettiere died after going into cardiac arrest following an overdose in South Carolina, where she was staying at an Airbnb with her most recent boyfriend Brian Hickerson, 37, and his brother Zach Hickerson, 38. 

In August, detectives confirmed to the Daily Mail that they responded to a 911 call from an 'acquaintance' of Panettiere, who described her as 'unresponsive.'

Narcan, a nasal spray used to reverse the effects of an opioid overdose, was found on a mattress in the loft apartment where the actress was staying, TMZ previously reported.

According to the Greenville Police Department's incident report, Zach told police that Brian was sleeping in a separate room of the Airbnb when he arrived and found the actress unresponsive in a chair.

Zach stated that Brian administered Narcan – a medication that reverses opioid overdoses – and that they performed CPR while communicating with 911 dispatchers.

In the wake of her death, Klitschko used Instagram to pay homage to his ex-fiancée.

He shared a photo of them with their daughter and added, 'Our family is going through a time of profound shock and grief.

'The announcement of Hayden's tragic death saddens me deeply. She left this world far too soon. Hayden was, although no longer my partner, an important part of my life and the mother of our daughter, Kaya.'

The Ukrainian boxer reflected on Panettiere's life as he added, 'She built an incredible career through immense talent, while also facing the darker sides of a very demanding industry. Nothing will erase the times we shared or the place she had in our lives.'

He concluded the heartfelt note, 'Rest easy, Hayden. May you find eternal peace.'

Days later, on what would have been her 37th birthday on August 21, he shared a portrait of the Nashville actress.

Klitschko wrote: 'Today is Hayden's birthday. Instead of celebrating the way we had planned, today we celebrate her life, her spirit, and the love she brought into this world.

'I want to thank all of Hayden's fans, friends, and everyone who has reached out for the incredible outpouring of love and support. At a time filled with so much sadness, your kindness has reminded me that there is still so much good in humanity.

'If you're reading this, I ask just one thing: even if only for a moment, think about LOVE. Reach out to a friend. Forgive someone. Be kind. Love is a superpower. Use it.

'Happy Birthday, Hayden. ❤️ You are loved, you are missed, and you will never be forgotten.'