I have point layer which represents GPS points along a transect line. I would like to randomly select 5 points along this transect, i.e. from this layer. 

Somehow I expected this to be straight forward, but I seem to miss something here. 

I used Research Tools --> Random selection within subset, selected the transect as input layer, Latitude as ID Field, Number of selected features (for the count instead of percentage) and entered 5 as number of selected features. After pressing "Run" it seem to process this ok, but then nothing else happens. I know there is no new layer created, but somehow I expected 5 random points along this transect to be selected and highlighted. 

Am I using the function in a wrong way or do I expect the wrong output?