Welcome to the Community. I'd be glad to assist you with reverting the deposit that was deleted by mistake.
If the deposit was manually made, you will need to remake it. Should the deposit have been made up of payments from the Undeposited Funds account, this money will have been returned to the account when it was deleted. If you need information about the deposit, you can review the Audit Log for more details. Here's how:
Select the Gear icon.
Click Audit Log.
Under Events, you will see Deleted Deposit for the item.
Select View, under History, for the deposit.
From here, you can review details for the transaction.
With a downloaded transaction, the steps are a bit different for reverting a deposit. When a transaction that was accepted from the Bank feeds is deleted, it will return to For Review. This transaction will need to be re-added. Here's how:
Select Banking on the left navigation menu.
Locate the deleted deposit and select Add/Match.
I've included a brief video as a demonstration for this:
If you should have any questions, please know that I'm only a post away. Have a wonderful day.