There's no scale to the drawing other than a "bastard scale" as we call it.
Using scale to fit, and using the randomly scaled title block as the plot area extents introduces variables to the plot scale multiple times, which makes it not a set scale.
The way I deal with it is usually take an engineer's scale and place it on a hopefully-round-number dimension like 50' or 100' or something, and try to match it up to tick marks on one of the scales, and jot down a note for reference, such as (1.2" = 100') or something. It's usually a very nasty number that requires a lot of calculator work to work with the drawing.
Otherwise I'd suggest LE's method, if you are trying to fix the 'problem'