Well, yes, if it was muted it shouldn't come through, so gain should be flooding the input (but nowhere else).
So taking it logically, you said you muted the the aux channels - did you try muting the actual input channel to make sure that the bass was coming through the channel you thought it was (caught me out once before), and also to ensure that it is not coming in another route as well, such as a microphone or something.
Once it is definitely coming in on only the channel you expect and you can control its levels, the meters in all the aux channels should tell you where it is getting to (and also as well as looking at the inputs in the aux channels, look at the outputs in the individual channel).
If it is getting somewhere you don't expect, then there is the channel matrix that is normally just a diagonal line but if it isn't, it can confuse everything
(I have never understood why anyone would want to edit this, would just lead to major confusion!)
Past that, looking in the overal meters screen should tell you where it is getting to