The sketch highlighted blue, because it had been selected as the profile to revolve (presumably was auto selected as the sketch done immediately prior to opennig the revolve tool, or was chosen from the Design Explorer).
Even if the last item sketched the blue sketch disappears when you click the revolve tool if sketches are not visible. So needs selecting to make the blue one visible. It still puts the Sketch No into the “sketch to be revolved” box if it were the last item on the list but you can’t see anything.
Might be something to look at for a future update, if the sketch No or name is in the box then have Alibre automatically make that sketch clickable.