Ah yes, It's very easy to overestimate how obvious things are to others. I found it by the way. But it took a few tries before I realised I had to use the interaction key to actually push. And also, I think it would have been more obvious (to me at least) if had been a box or something. You always push boxes around (unless you can break them for goodies). :)
But these are things you learn by playtesting. Especially puzzle games require lots of letting other people play, which there is not much time for during a jam (until now during the rating that is).