Hopefully you have a recent backup that you can restore.
Restore your Quicken data file from a Manual or Automatic Backup taken prior to the problem first occurring, if necessary going back to older backups until you find a file that does not exhibit these symptoms.
Windows: https://www.quicken.com/support/how-backup-or-restore-your-quicken-data
Mac: https://www.quicken.com/support/mac/how-backup-or-restore-your-quicken-data
In addition to the backup files Quicken generates, if you use your Mac's Time Machine to continually back up your Mac, you should be able to retrieve a copy of your Quicken data file from prior to your inadvertent deletion of the account. Time Machine backups give you hour-by-hour backups for the past week, so you should be able to zero in to just before the problem.