Mitch Garabedian, a civil attorney for the accuser, said in court papers filed Wednesday that after an extensive search, the accuser and his family cannot locate the phone.
Spacey's attorneys have publicly accused the alleged victim in the case and his mother, a former anchor at Boston ABC affiliate WCVB, Heather Unruh, of deleting key text messages that could potentially exonerate the actor from the phone before turning it over to police.
At a contentious hearing earlier this month, Spacey attorney Alan Jackson said that Unruh told police that she had cleaned the phone of her son's "frat boy activities" before turning over the phone to police for a forensic analysis.
That analysis turned up inconsistencies between screen shots the accuser sent to police and the extraction report completed by prosecutors, Jackson said.
The accuser and his family "have searched all the places where such a phone may have been stored," Garabedian wrote in court papers filed on Wednesday. "They have not found the phone."
In response to the filing, a Nantucket District Court judge postponed a scheduled June 21 hearing until July 8, and told attorneys that if the phone cannot be located by then, the accuser will be asked to testify about its whereabouts in court.
In new court motions filed late Thursday and first reported by The Boston Globe, Spacey's attorneys reveal new exchanges between the accuser and his friends, apparently on the night of the incident.
The exchanges appear to begin mid-conversation, as the alleged victim tells his then-girlfriend and others on a group chat that Spacey is making romantic overtures to him.
"Sounds like he's hitting on you...."
"I think he is" — "He's grabbing my leg and [expletive]," the accuser texted back, according to the court filing.
Later, the man types, "I'm not gay" — "But I think spacey is."
His then-girlfriend writes back, "Hahaha" — "Uhg literally so jealous" — "Plz take a selfie with him at some point."
The man texts back, "No I'm serious no" — "Now" — "He's totally gay."
"Wait what..." the girlfriend responds. "For real?"
"He's grabbed my [expletive] like 8 times," the accuser texts back, according to the new court filing.
"He's pissed I'm texting I" — "I told him I had a gf."
His girlfriend expressed skepticism, writing back, "I thought you were serious" — "Taking advantage of my gullible-ness."
The man replies "No I'm serious" — "He's gay" — "He pulled my zipper down" — "And he invited me to his house" — "I'll talk to you later."
She texts back, "What the [expletive] is happening," followed by a message containing three flushed-face emojis, then a message and a warning.
"Have fun but not too much fun if you know what I mean."
The final section of the thread lists 18 consecutive messages issued by the accuser to his friends.
"Jesus Christ he reached down my pants."
"No this is Kevin ducking spacey"
"He's buying me yet another drink"
"He's gotten me so many"
"[Girlfriend's first name]"
"He grabbed my [expletive]"
"Kevin spacey is gay"
"I'm gonna get the pic"
"I got the autographs and a hell of a stout"
Earlier this month, Spacey's defense attorneys sought to convince a judge that the phone had been scrubbed of potentially exculpatory missives, in arguing for the defense team's need for access to the actual phone itself.
"At 1:41 a.m. [on July 8, 2016] there was a text, according to the forensic report, that [used the alleged victim's first name, that urged him] to "leave and go home," Jackson said in court. In response, according to Jackson, the alleged victim texted back, "‘Should I, actually?'"
Portions of subsequently-deleted text exchanges cited by Jackson turned up the words "picture" and "help," according to the attorney.
Before "he handed the phone to police, he deleted the entire message except the word 'help'," Jackson contended. "Their extraction report only shows 'help.' That's the kind of cleansing [the accuser] and Heather were undertaking."
In court papers, Garabedian said that authorities returned the phone to the father of the victim after completing a forensic exam of the contents. The father, according to court papers, said he has no memory of receiving the phone.
Legal experts said that paper trails usually follow the movement of criminal case evidence.
"You would, generally, when turning back evidence that's involved in an active criminal case, you would expect there to be a receipt of the property turned over," said Stewart Ryan, a former Montgomery County prosecutor in Pennsylvania, who successfully convicted Bill Cosby of sex assault charges last year.
"At least in my experience, those receipts are signed by the law enforcement officer turning it over and the person who receives it."
A spokesperson for the Cape and Islands District Attorney Michael O'Keefe declined to respond to a question from ABC News about whether a receipt for the phone or any other record was issued to the accuser's father by local authorities, or otherwise generated in law enforcement records.
If the phone cannot be located by July 8, Nantucket District Court judge Thomas S. Barrett wrote in an order this week, the accuser, his mother and Garabedian "shall appear [in court] and give testimony on the whereabouts and condition of the subject phone."
Attorneys separately representing Spacey and his accuser did not immediately respond to requests for comment on the new twists in the case.
ABC News' Matt Foster contributed to this report.