QueryString funcionability in code project only

Greetings fellows

I have an inquiry about a funcionability in a project . They put sensible data in the url, like reservationCode and therefore I can’t assure if the this data is sent by https. because the proyect is only code nothing else.

the project is in charp. should I look in the config files like config.asax ?

Even if the application is using HTTPS, sensitive data should not be send in the url because that data could be saved in the browser’s history.

What “sensible” data are they transferring on the url?