Do you live in an area where cellular coverage is a challenge? Here’s why I ask: On our legacy phones (including the Moto E 2nd Gen), we first send the text message by data - if your phone is on Wi-Fi or has a cellular data connection it will receive the text message. If the phone is off, on airplane mode then it doesn’t have access to data. When that method of delivering the message fails, the message delivery moves to the traditional method using the cellular voice channel. At that point, if you don’t have a cellular connection, you will not get the text message. If you move into an error with cellular coverage before the text message times out, you will receive it.
So it would be quite possible, if you’re in an area with no cellular coverage, to disable data (airplane mode or phone turned off) miss a message, re-enable data (turn the phone on and connect to Wi-Fi) and send and receive text messages but not receive the missing one that has already failed to the cellular voice channel. But later, when you move to an area with cellular coverage before the failed text message times out, it will be delivered to the phone.
As @jamesr.cqtjca pointed out, switching to Republic Anywhere as your messaging app would help with this issue, because Republic Anywhere delivers your text messages over data, so the messages would never permanently fail to the cellular channel.