United admitted that a deal for the forward fell through after they failed to conclude the transfer before Monday's 5pm deadline.
The club said a fax was sent to the Football League confirming the deal but it arrived at 5.14pm, 14 minutes after the January transfer window closed.
The Premier League extended the time allowed to register any transfers affected by the severe weather which swept across England on Monday, but the Football League did not follow suit.
United chief executive Shaun Harvey said: "It is disappointing that the Football League stuck rigidly to the 5pm deadline when you take into account the exceptional circumstances that prevailed.
"The FA Premier League made arrangements for their clubs to register players after the deadline and if the Football League had adopted the same approach then Liam Dickinson would be a Leeds player until the end of the season."
The club said a fax was sent to the Football League confirming the deal but it arrived at 5.14pm, 14 minutes after the January transfer window closed.
The Premier League extended the time allowed to register any transfers affected by the severe weather which swept across England on Monday, but the Football League did not follow suit.
United chief executive Shaun Harvey said: "It is disappointing that the Football League stuck rigidly to the 5pm deadline when you take into account the exceptional circumstances that prevailed.
"The FA Premier League made arrangements for their clubs to register players after the deadline and if the Football League had adopted the same approach then Liam Dickinson would be a Leeds player until the end of the season."