I still struggle with "ci". I had understood it to mean "there", sometimes, or "us", but can also be used before a transitive verb conjugated in first person plural to make it reflexive "ourselves". In this case, both stiamo and pensando are intransitive, so I would think that "ci" isn't necessary, and it doesn't seem to mean "there", which makes me think it's the accusative "us" ... but this also clearly wrong, since "us" doesn't appear in Duo's translation, so I'm stumped.
You're right! According to https://en.wiktionary.org/wiki/ci#Italian "ci" can also mean "on it, about it, of it"! I don't think this was ever really explained to me before, except perhaps implicitly. I wonder if remembering that "ci" descends from Latin "look here" and "look there" can help one remember its many uses? Probably not.