Blackpool had agreed a fee with Pompey for Nugent, 25, but were unable to locate him as the transfer deadline closed in.
"If the player hadn't gone missing we'd have had David Nugent. With 20 minutes to go we had Nugent signed on, but no one could locate him, so he couldn't sign his contract and it all fell through," Ian Holloway, the Seasiders manager, told the Blackpool Gazette.
"So that's one that wriggled out of the net, but it happens. I thought he was one that was worth trying to get, so because of that we put some other deals on hold.
"Nugent was the main one we targeted. We didn't miss many, but unfortunately that was one we did and it wasn't possible to get a back-up with 20 minutes left."
Leeds United are giving a trial to the Senegalese midfielder Amdy Faye, who is a free agent having been released by Stoke City in the summer.
He has been training with the club and will feature for their reserves against Grimsby Town's second string on Tuesday night.