I read elsewhere on this forum (I think) about an app from the Play store, "Shush". When you mute your phone, it pops up a little screen asking for how long, and after that time, it switches the ringer back on. No more missed calls because I forgot to put the ringer back on. (I am not affiliated with this dev or app at all - just a happy new user!)
Link to Shush
Link to Shush

