Here I found an example of how you can do it
There are other cloud schedulers out there which are more reliable and more production-grade than Heroku Scheduler. Cron To Go is one such scheduler that is also an Heroku add-on (full disclosure, I work for the company that created it). It allows you to use cron expressions to run your code on Heroku one-off dynos. You can also get email and webhook ...
If you were using Heroku Postgres, it's possible Heroku could restore it from some internal backup, Since you do not have that I highly suggest you reach out to support. They have some possible recovery tools, but you must go through support and time is of the essence... the news might not be good if you’ve never done a backup.