Hmm, your grocery store sounds more interesting than mine. They only have run-of-the-mill plants here.
Leonotis are regularly misidentified even when they do have a label. It seems that 90% of the time things listed as Leonotis menthifolia or Leonotis leonurus are actually Leonotis nepetifolia. Leonotis nepetifolia sets a lot of seeds and can be a bit weedy in some areas. It is pretty, though, and the hummingbirds like it.
Fingers crossed for your next Leonotis leonurus!