Barca was dealt a severe blow this week when it confirmed Ousmane Dembele is expected to be out for six months after hamstring surgery.
With Luis Suarez also sidelined, Barca is reported to have been granted special dispensation to sign a replacement, providing the player in question is either a free agent or already based in Spain.
Willian Jose, Angel Rodriguez, Lucas Perez and Loren were said to be their chief targets, although a reported €12 million ($19.4 million) budget limits it significantly.
Rubi admitted Barca did make an approach for Loren but was unsuccessful, with Betis not willing to let the player go.
"Loren is going to end the season with Betis," Rubi said of the striker who has scored eight LaLiga goals in 22 appearances this term.
"They have asked, but the operation is 99 per cent not done. We don't want him to leave and they have looked at many [players].
"Loren trains just as well as always. This is something that happens in football.
"We couldn't sign another player unless his release clause is paid. Loren's €50million, so 99 per cent it is not done.
"The information I have is that he is [staying] here and that is what we all want."
Loren, 26, was given his league debut for Betis by current Barca coach Quique Setien in February 2018.