I’ve seen products such as the Trackr pixel out there which make your phone ring if you’ve lost it, even if it was on silent. I thought I’d share a free alternative to this.
All you need is a free account with If This, Then That. Once you have an account, you can set up this applet.
Essentially, when your phone receives a text with a specified keyword/phrase, its ringtone will be turned up to max volume.
Edit: If you have an Alexa or Google Home, there are also more direct ways to find your phone via the same site here and here, respectively.