As I understand this; if a person applies for flood insurance within the 13 month period after the remapping the 30 day waiting period is waived. If applied for in the 14th month then the 30 day waiting period is in effect except for those exemptions given in connection with a loan against the property.
You are not required to monitor your portfolio, and a remapping is not a tripwire for you to review your portfolio, but once you become aware the property is located in a SFHA, either by a portfolio review or a LOL monitoring notification, you must notify the borrower of the need to get flood insurance. See page 5 of the MPFIG
During the term of the loan, ensure that flood insurance is maintained or obtained if the lender becomes aware that the building involved subsequently becomes part of an SFHA; and
Until FEMA issues the LOMA/R your borrower must obtain flood insurance. If FEMA issues the LOMA/R then the full premium will be refunded to your borrower.
The opinions expressed are mine and they are not to be taken as legal advice.