If you receive notice of a forgery (or other item being returned), those are not collected funds. It is my understanding that you can place a hold in these instances to protect against a loss, but you must notify your customer.
In the case of an item posted to a wrong account, I don't see a reason to impose a hold. You may just need to move or revoke the credit, and be sure your customer is aware of why you need to make the adjustment.
We had a situation once when a new customer was bringing checks payable to her business that she had clearly altered by crossing out the business name and writing her name for deposit to her personal account. When the branch manager discovered the transactions, she reversed the credit to the account and declined to process the checks. We had to explain to the customer why her activity was not acceptable.
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To avoid criticism do nothing, say nothing, be nothing. ~Elbert Hubbard