This happened to me as well with Uber. They use SMS 2FA and didn't provide any backups. I left my phone in an Uber and I couldn't log into my account to notify the driver because 2FA was in place. I also couldn't contact Uber about the issue because they try as hard as possible not to provide customer service mechanisms for people to leverage.

At the end of the day I had to use another friend's Uber account to contact Uber and explain the situation. They disabled 2FA and let me back into my account. I suppose Uber could validate the GPS position of the driver and my phone and use that to validate my story, but I doubt they went through all that trouble :(