No, there is nothing that can take the place of the pass as an official document entitling you to travel.

I would say that the most important thing you can do is to not lose or have your phone stolen. Having a particular place to always keep your phone that is secure from pickpockets would be a very good start, too many people drop all sense of personal security while on holiday, unfortunately in many tourist hotspots professional thieves know exactly how to spot easy marks.

Customer services can be contacted here https://eurail.zendesk.com/hc/en-001/requests/new?

Should you loose or break your phone, then contact customer service via the form mentioned, mention your pass numbers and that you are currently travelling (both are important to mention). They will then disconnect the passes from your lost/broken phone, so you can connect them to another phone. If you're travelling, a response is normally quite quick, within a few hours.

If you would loose your phone and need to travel before Customer Support has managed to help you, you need to purchase a ticket for that travel. Such a ticket will not be refunded by Interrail.