The Italian left-back, 22, had struggled to settle in Cumbria and returned home in December in an effort to secure a deal with a new club.
"As far as we understand things he's still having trials, but we needed him to make a decision before the transfer window closed," Carlisle's managing director John Nixon said.
"He hasn't settled over here so the best thing for all concerned was to allow him to leave and try to secure himself a deal over in Italy."
Bugno arrived at Brunton Park in July and made four first-team appearances before losing his place in Greg Abbott's side.
