Please help...

I added a video effect to my movie (it was 'Threshold')...didn't like it...but now I cannot get rid of it.  Tried the undo button...that didn't work.  zoomed in on the video timeline so as to select it (& then delete it); & cannot find it.  I need to get rid of this effect, otherwise I'll have to start all over again...adding my movie, then titles, text...everything.

thanx in advance,

MWF
(using Vegas Movie Studio 16 Platinum)