On the contrary, the media insisted for weeks the referendum was "too close to call", citing endless polls that generally favored the 'no' vote, but were close to 50-50. Obviously people vote more conservatively when it matters.
Meanwhile, the bookmakers, who actually had skin in the game, knew a 'yes' vote was unlikely, and reflected that in their odds.
They were biased because they consistently took a negative stance towards the potential ramifications (not chance of outcome) of independence.
The possibility of Scotland voting for independence had that in spades; nobody really knew what it would entail.
Thus the media persisted in presenting it as a realistic, likely prospect, even when it was quite apparent (as per bookmakers odds) that a 'yes' vote was very unlikely.
(I don't know either way, not being paying much attention to the press, though BBC Scotland has seemed quite balanced)
If the media, who overwhelmingly supported No were reporting it as "too close to call" then either a) they felt that was the most effective way to bring about the result they desired, or b) they are idiots who don't understand the basics of the things they report on. Probably a little of both.