No, if one swipes away (inadvertently or intentionally) the associated notification it will disappear. Generally, toggling WiFi is sufficient to bring it back.
Have you checked Android settings to see which apps used those large amounts of data on the days in question?
The Republic arc icon is intended to provide a quick reference of the state of WiFi calling and text messaging. It is not intended to serve as an indicator of whether or not one is connected to a WiFi network per se though it can serve as a proxy for that to some extent. For example, when out, about and away from WiFi, the arc will be hollow with the associated notification advising one is connected to the cellular network. When on WiFi, the arc is generally solid. Neither of these states speaks to persistence (whether the arc is there or not). Some detail here: