Hi, I'm Robert and I'll be helping you with your financial software question.
I am very sorry but there is no "undo" button in quicken. No way to just say woops let me get that back in one easy step.
You can do 1 of 2 things.
1. Restore a backup file that hopefully you made when it asks you to all the time.
Hit File menu
select backup and restore
select restore a backup file
select the backup file to restore. Chose one from before you deleted the account
you will lose everything that you did between the time you made the backup file and now.
2. Re create the account the way you did when you first made it.
Tools / add account
follow the prompts to select account type and bank and your id and password XXXXX
It should download the last 90 days of transactions from your bank. Anything before that you would have to either put in manually or you might be able to import if you go to the banks website through the internet browser and create a report to be downloaded in quicken web connect format. Remember where you save that file when you download it. within quicken go to file / import / select quicken web connect
browse to the file that you saved and select it.
everything in the report that you downloaded from the bank should get added to the account.