Although some pianists might be able to get away with playing on autopilot(this is not a commonly used word to describe playing so people may have different ideas about what this means), I think most pianists will play much better if they learn to have excellent concentration while playing. Although it's possible their minds are not concentrating on the music, most professional pianists give the impression of a very high level of concentration while playing at least most of the time.
To avoid memory slips and the performance anxiety this often causes most people find muscle memory alone insufficient. I think most people automatically use some degree of auditory memory in addition to muscle memory, and there are, of course, additional memory techniques besides those two.
But the best way to avoid and really eliminate any memory issues is simply to play with the score. I think, especially for most amateurs, the pros of playing with the score far away any cons. Even without some electronic device to turn pages on an iPad there are many tricks that allow one to turn one's own pages without pause. I know this from my own experience. Some people find playing with the score difficult because they have not learned how to look back and forth between the keyboard and the score. In that case, I think this incredibly important skill should be practiced more.