Pretty much that. I got my super privileges when one super was working and went to break, or lunch.
He told me I was in charge while he was away and it turned out he gave me the privileges.
Told my CSM the next day, half expecting him to take them off me, but he got someone to show me around the super menu, so I'd know what I was doing.
I did my back in at one point, and was on light duties, so had to stay in the smokeshop. Often when it got busy I was on smokeshop and super, while my CSM was on register.
I was sort of forced to become a decent supervisor at that point, as I was full time, and pretty much spent the whole time supervising.
Kept it up with checking storenet for things I wasn't sure of, etc, and became our 3ic by being the most competent person there, often being better than CSM or 2ic, but without the stress.
Didn't need to do it by assertion, I don't feel threatened or annoyed when other supervisors take charge over me, unless I'm in a shit mood to begin with.
They usually come asking me how to do something relatively simple anyway, stuff isn't something most are trained to do.
Also finally finished my Certificate II in retail operations the other day, so now I have a pretty good chance of being promoted to 2ic somewhere, but I'm not sure if I really want that, as now I spend half my time in cash office, and I don't want to lose that.
It was out CSM's 30th anniversary with woolies today. Came in to work to attend, and for the free food. To work that long at I'd have to keep working there for as long as I have already lived in addition to my already 4 years.
Told him that and he felt old.