The Premier League window shut at 11pm on Tuesday without Pope completing a move, after the England international was told he no longer figured in new manager Matthias Jaissle's plans.
Pope had featured in all three of Newcastle's summer friendlies under previous manager Eddie Howe, but has not been involved in a single matchday squad since Jaissle's arrival, with summer signings Lukas Hornicek and Ewen Jaouen both established above him in the pecking order.
Tentative interest from Hull City, Ipswich Town and Leeds United never developed into a concrete offer, leaving Celtic as one of the more persistent links throughout the closing weeks of the window.
The Scottish champions had been searching for competition for Finland international Viljami Sinisalo following Kasper Schmeichel's retirement, but ultimately turned to Wolverhampton Wanderers goalkeeper Sam Johnstone instead, completing his season-long loan move on deadline day.
Celtic manager Martin O'Neill explained the decision to bring in Johnstone rather than pursue Pope further.
"We are really happy to welcome Sam to Celtic," O'Neill said. "He is a quality keeper with excellent experience at the highest level and I think he will be a very good addition to our goalkeeping team. He is really looking forward to joining Celtic, to add competition to our team and we are pleased to bring a goalkeeper of this quality to the club."
With Johnstone's arrival closing off Celtic as a destination, Pope is now more than likely to remain on Tyneside until at least the January window, with his prospects of first-team football in the meantime looking remote. Jaissle addressed the situation directly with the goalkeeper during pre-season.
"I had a talk with Nick," the head coach said. "I really appreciate what he has done in his career so far. He knows exactly the situation right now, and we need to deal with it in the best possible way."
Pope, who is under contract at St James' Park until the end of the season, could still find a way out through one of several transfer windows that remain open elsewhere in Europe, including Belgium, the Netherlands, Portugal and Turkey.
However, there has been no indication of concrete interest from any club in those countries so far, leaving Newcastle facing the prospect of carrying a high-earning, experienced goalkeeper with no realistic path to regular football for the first half of the campaign.
Newcastle United's overhaul of the goalkeeping department has been one of the more significant transformations of any single position at the club this summer, with Aaron Ramsdale's loan not extended and John Ruddy also departing before Hornicek's arrival from Braga and Jaouen's move from Reims were completed.
That leaves the club with a considerable financial outlay tied up in three senior goalkeepers competing for essentially two active roles, with 19-year-old academy prospect Aidan Harris having occupied the third-choice slot under Jaissle before Pope's own situation became clearer following the completion of the transfer window.